The chemical used in the high-profile killing of the stepbrother of North Korean leader Kim Jong-un has been identified as the Vx nerve agent, Malaysian police reported.

Vx is a highly toxic substance used for chemical warfare and is classified as a weapon of mass destruction by the UN.

Malaysian authorities say Kim was killed w/ VX Nerve Agent. Considered a weapon of mass destruction by UN. 10 mg through skin contact fatal. pic.twitter.com/E8MDUSYwRE — Yashar (@yashar) February 24, 2017

The Malaysian police said traces of Vx were identified in a preliminary lab report conducting forensic analysis of the evidence found at the crime scene.

Swabs were taken from an eye and the face of the killed North Korean man by the chemistry department of Malaysia, the police said the Inspector General of Malaysia Khalid Abu Bakar said in a press release.

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The police chief also said investigators were trying to establish the source of the nerve agent, including whether it was imported or produced in Malaysia.

“We are investigating it,” he told reporters on the sidelines of an event. “If the amount of the chemical brought in was small, it would be difficult for us to detect.”

He also said that one of the two women arrested in connection with the killing had suffered from the effect of the toxin.

“She was vomiting,” he said, declining to elaborate.

Kim was killed by a poison last week after two female suspects assaulted him at Kuala Lumpur airport. He was travelling incognito to Macau, where he had been living for years in exile.

The airport where the attack took place will be decontaminated, Malaysian authorities said.

Khalid added that the police would sweep the locations where the suspects were for “radioactive material” without explaining why he believed any could be found. Vx is normally not radioactive, and the Malaysian authorities never mentioned any radioactive contamination possible in the case.

VX, the banned nerve agent used to kill Kim Jong-Nam, is one of the deadliest chemical agents ever manufactured https://t.co/c19E3R7RL9pic.twitter.com/dflpfgHI99 — AFP news agency (@AFP) February 24, 2017

Vx is one of the deadliest chemical weapons that can be used in a liquid, cream or aerosol form. Depending on dosage and whether it was inhaled or applied to the skin, it can kill as quickly as in 15 minutes or over several hours.

Producing Vx does not necessarily require government involvement, as evidenced by the Japanese doomsday cult Aum Shinrikyo, which manufactured a small amount of the agent and used it in attacks on three people, one of which resulted in the death of the victim.

The chemical has been featured in several popular movies and TV series, most prominently in the 1996 film “The Rock,” starring Sean Connery and Nicolas Cage. The dramatic and inaccurate way Vx was shown in the movie – stored in glass containers – inspired a false description of Saddam Hussein’s chemical weapons program, which was part of the justification for the 2003 invasion of Iraq.