There is a growing belief within the US government that the Islamic State militant group is making and using crude chemical weapons in Iraq and Syria, a US official has told the BBC.
The US has identified at least four occasions on both sides of the Iraq-Syria border where IS has used mustard agents, the official said.
The official said the chemical was being used in powder form.
A BBC team on the Turkey-Syria border has seen evidence backing these claims.
The US believes the group has a cell dedicated to building these weapons.
"They're using mustard," the individual said of IS. "We know they are."
The mustard agent was probably being used in powder form and packed into traditional explosives like mortar rounds, the official said.
"We've seen them use it on at least four separate occasions on both sides of the border - both Iraq and Syria."
When these weapons explode the mustard-laced dust blisters those who are exposed to it.
What is mustard agent?
The term "mustard gas" is commonly used to describe the agent, but it is liquid at ambient temperature.
Sulphur mustard sometimes smells - like garlic, onions, or mustard - and sometimes has no odour. It can be clear to yellow or brown.
People can be exposed through skin contact, eye contact or breathing if it is released into the air as a vapour, or by consuming it or getting it on their skin if it is in liquid or solid form. It causes blistering of the skin and mucous membranes on contact.
Though exposure to sulphur mustard usually is not fatal, there is no treatment or antidote to mustard which means the agent must be removed entirely from the body.
The official said the intelligence community believes the most plausible explanation is that they are manufacturing it.
"We assess that they have an active chemical weapons little research cell that they're working on to try and get better at it," the official said.
The official said knowledge to make the mustard agent is widely available, and it is not a complex chemical to produce.
The alternative theories are that IS militants found chemical weapons caches in Iraq or in Syria.
It is unlikely that militants found the chemical agent in Iraq, the official said, because the US military would have probably discovered it during the military campaign it waged in the country for about a decade.
The official said that militants were unlikely to have seized the chemical agent from the Syrian regime before the regime was forced to hand over its stockpile under the threat of US air strikes in 2013.
The US government's position continues to be that it is investigating claims of chemical weapons use in Iraq and Syria, but the official speaking to the BBC said that many intelligence agencies now believe there is now enough evidence to back up these claims.
The official requested anonymity because that person was not authorised to speak about it publicly.
In recent days, the BBC's Ian Pannell, working from the Turkey-Syria border, has seen new evidence of chemical attacks being carried out in Syria - potentially by the regime and rebels.
Syria is supposed to be free of chemical weapons after a UN-backed deal that saw the Syrian government hand over 1,180 tonnes of declared toxic agents and precursor chemicals to the Organisation for the Prohibition of Chemical Weapons (OPCW).
That process began in October 2013, and was completed by June of the following year.
More than 200,000 people have died since the Syrian civil war began following anti-government protests in early 2011, but only a tiny percentage are believed to have died as a result of chemical weapons.
Last month, the UN launched an investigation to determine which individuals, groups or governments are involved in the use of chemicals as weapons in Syria.
And that same month, the US military said tests on IS mortar fragments from fighting in Iraq showed traces of chemical arms.
US Brig Gen Kevin Killea said in late August that the US had found traces of the chemical agent sulphur mustard on mortars used by IS to attack Kurdish forces in northern Iraq.
At the time, however, he also said that the tests were not conclusive and final testing was needed.
He described sulphur mustard as a Class 1 chemical agent, one that is rarely used outside of chemical warfare.
Involvement of community elders, monitoring of radical social media platforms and real-time sharing of information are a few steps government plans to take to prevent youths getting attracted to radical ideologies, such as that propagated by ISIS.
A high-level meeting today, chaired by Union Home Secretary L C Goyal, formalised a strategy to neutralise extremist ideologies such as that espoused by ISIS, which has influenced thousands around the world. Counter-radicalisation efforts would include counselling of youths, convincing community elders to persuade the younger generation to not get influenced by any extremist ideology besides others.
The focus would also be on how to quickly respond to any report of youths planning to join terror groups like ISIS and how to prevent Indian youths from coming under the sway of extremist doctrines, official sources said.
DGPs and Home Secretaries or their representatives of a dozen states including Jammu and Kashmir, Uttar Pradesh, Andhra Pradesh, Telangana, Karnataka, Maharashtra, Kerala, Assam, Punjab, West Bengal and Delhi (Commissioner of Police) attended the meeting.
“Attraction towards radical ideology of any religion is a matter of concern. We are in the process of putting in place a robust system to counter radicalisation of Indian youths,” a source said.
According to an official estimate, around 25 youngsters have been identified across the country as having been attracted to the idea of ISIS and wanting to join the group. A Home Ministry statement said the meeting was held to sensitise the states about the existing and emerging threats to internal security situation in the country.
The meeting was held to further streamline the institutional mechanisms for sharing information and to adequately meet the threats from terrorism, the statement said. The meeting decided to strengthen the capacity building of the police officers in states through training programs, to be organised by central intelligence and security agencies. “Some instances of radicalisation of youth in some states came up for discussion. Appropriate measures on counter radicalisation including counselling of such youth and their families were also discussed,” the statement said.
The meeting also looked at the modalities of analysing the suspected social media platforms run by terrorists and criminal outfits, it said. In Telangana, 17 youths have been prevented from travelling to Syria and, recently, four from Maharashtra were also stopped from travelling to the Middle-East.
Sources said that although none of the youths were arrested, they were kept under surveillance. They went through counselling and are living normal lives. Maharashtra and Telangana have already put in place a model for dealing with ISIS-related cases. While there have been arrests in some cases, agencies realised that arrest should not be the first option.
Monitoring of social media has already begun, sources, meanwhile, said, adding that efforts would be made to gain the confidence of the Muslim community. Till now, 11 Indians have been identified who joined ISIS, of whom five are reportedly dead.
An Australian airport website was offline today after being taken over by pro-Islamic State hackers who published messages supporting the jihadist group.
Police said hackers appeared to have targeted the web host used by the Hobart International Airport in Tasmania and not the facility itself, and no direct threats were made.
“A message placed on the site contained a statement supporting ISIS,” Tasmanian police said in a statement, using another acronym for the radical group commonly known as IS.
Authorities said identical messages had appeared on websites around the world since late 2014.
“The group claiming responsibility for the hacking appear to non-discriminately target organisations who use web hosts such as the one used by Hobart International Airport,” police said.
Officials were notified that the website had been defaced yesterday morning, with the site remaining down today.
“Tasmania Police have been monitoring activity at the airport premises, and there has been no suggestion of targeted activities on-site,” they added.
The airport’s operators said website security was being reviewed with the IT service providers.
Australia is involved in the US-led coalition against IS in Iraq and has increasingly been sounding the alarm over radicalised citizens, with about 90 thought to be fighting with the Islamic State group in Iraq and Syria.
All of the country’s main carriers fly into Hobart, the state capital, including Qantas, Virgin Australia, and Jetstar.
It retains the name “international airport” despite no longer offering scheduled overseas flights.