The poison used to kill the estranged half brother of North Korea’s leader at a crowded air terminal in Malaysia was the banned chemical weapon VX nerve agent, police said Friday. Eleven days after the deadly toxin was used, they said they would eliminate any possible remaining trace of it from the airport and other locations.

The revelation that VX nerve agent, deadly even in minute amounts, was used in the Feb. 13 attack boosted speculation that Pyongyang dispatched a hit squad to kill Kim Jong Nam, the outcast older sibling of North Korea’s ruler.

The case also raised questions about public safety, although there was no sign that any bystanders had fallen ill. Police said one of the alleged attackers had been vomiting in the hours after the attack, but there were no reports that anyone else had been sickened.

Police had gone more than a week saying the airport was safe, even though it had not been decontaminated after a mysterious and deadly poisoning. After the announcement that VX was to blame, The Associated Press asked Malaysia’s Inspector-General of Police Khalid Abu Bakar in a text message whether decontamination would take place. He responded, “We are doing it now.”

He later said police were arranging for the atomic energy agency to decontaminate the airport and “sweep all locations which we knew that the suspects went to.”

Asked if people should avoid the airport because of fears of contamination, Khalid said, “No. No. No. But I don’t know. I am not the expert.”

VX nerve agent was detected on Kim’s eyes and face, Khalid said earlier in a written statement, citing a preliminary report from the country’s Center for Chemical Weapons Analysis.

According to Malaysian investigators, two female suspects coated their hands with the liquid toxin and wiped it on Kim’s face as he waited for a flight home to Macau, where he lived with his family.

Kim sought help from airport staff but he fell into convulsions and died on the way to the hospital within two hours of the attack, police said.

Malaysian police say the women – one Vietnamese, one Indonesian – washed their hands immediately after the attack as they’d been trained to do, and had practiced the attack in Kuala Lumpur shopping malls.

Malaysian police had initially said no one besides Kim Jong Nam had been sickened. But Khalid told reporters that one of the two women accused of wiping the toxin on Kim’s face became sick later and suffered from vomiting. He declined to say which woman had been sick but said she is no longer under treatment.

Khalid said police were still investigating how the lethal nerve agent entered Malaysia.

VX nerve agent has the consistency of motor oil and can take days or even weeks to evaporate. It could have contaminated anywhere Kim was afterward, including medical facilities and the ambulance he was transported in, experts say.

Dr. Bruce Goldberger, a leading toxicologist who heads the forensic medicine division at the University of Florida, said even a tiny amount of VX nerve agent can be fatal. An antidote can be administered by injection. U.S. medics and military personnel carried kits with them on the battlefield during the Iraq war in case they were exposed to the chemical weapon.

“It’s a very toxic nerve agent. Very, very toxic,” he said. “I’m intrigued that these two alleged assassins suffered no ill effect from exposure to VX. It is possible that both of these women were given the antidote.”

He said symptoms from VX would generally occur within seconds or minutes and could last for hours starting with confusion, possible drowsiness, headache, nausea, vomiting, runny nose and watery eyes. Prior to death, a victim would likely have convulsions, seizures, loss of consciousness and paralysis.

The toxin was almost certainly produced in a sophisticated state weapons laboratory, and is banned under an international treaty. But North Korea never signed that treaty, and has spent decades developing a complex chemical weapons program that has long worried the international community.

Outside experts believe North Korea has the capacity to produce up to 4,500 metric tons of chemical weapons a year, and could raise that to 12,000 tons during a crisis. Its current inventory has been estimated at 2,500 to 5,000 tons.

It is suspected of being particularly focused on mustard, phosgene, sarin and V-type chemical agents – substances including VX that are designed to poison through contact and remain lethal for long periods of time. The North’s development of such agents has been of special concern because of fears it might try to put them in artillery shells for an attack on South Korea’s capital, potentially threatening the lives of millions.

Joseph Bermudez, a well-known North Korea analyst, wrote an article for the respected 38 North website in 2013 that said the North is capable of not only employing “significant quantities and varieties of chemical weapons” across the Korean Peninsula but also using those weapons worldwide “using unconventional methods of delivery.”

He also said there is a “growing body of evidence” indicating the North has shared chemical weapons capabilities with Syria, Iran and others.

In addition to the suspected attackers, Malaysia has arrested a North Korean man said to be an information technology worker at a Malaysian herbal supplements company and is seeking at least seven people, including the second secretary of North Korea’s embassy in Kuala Lumpur.

Kim Jong Nam’s very public assassination has unleashed a diplomatic crisis. North Korea has denounced Malaysia’s investigation as full of “holes and contradictions” and manipulated by Pyongyang’s enemies.

Malaysian Foreign Minister Anifah Aman pointedly defended his country’s work on Friday, saying at a news conference, “The entire world knows that the investigation has been objective, impartial and also transparent.”

He said the North Korean ambassador “continues to be delusional and spew lies and accusations” about the Malaysian government, and noted that Pyongyang’s top diplomat in Kuala Lumpur “must realize that he must enjoy the confidence of the government of Malaysia.”

(AP)