Thomas Maresca

Special for USA TODAY

SINGAPORE — VX nerve agent, a highly toxic chemical, was used to kill Kim Jong Nam, the estranged half-brother of North Korean leader Kim Jong Un, Malaysian police said Friday.

Police Inspector-General Khalid Abu Bakar said the substance was identified in a preliminary report by the department’s Center for Chemical Weapons Analysis.

Kim Jong Nam died Feb. 13 shortly after two women put the substance on his face while he was checking in for a flight at the Kuala Lumpur airport in Malaysia's capital.

The report identified the substance as ethyl N-2-Diisopropylaminoethyl Methylphosphonothiolate, or VX nerve agent. It is a chemical agent classified as a weapon of mass destruction by the United Nations.

Traces of the nerve agent were found from swabs of the face and eyes, the release said.

VX is the most lethal of nerve agents, according to the U.S. Centers for Disease Control and Prevention. It is considered much more toxic than sarin by entry through the skin. “It is possible that any visible VX liquid contact on the skin, unless washed off immediately, would be lethal,” the CDC says on its website.

A dose of 10 milligrams on the skin is enough to be fatal. The production and stockpiling of more than 100 grams per year was outlawed by the Chemical Weapons Convention of 1993. North Korea, however, is one of six countries that are not signatories to the convention.

Malaysian authorities also claim that one of the women accused in the attack suffered from vomiting after wiping the agent on Kim Jong Nam's face. Bakar declined to identify which woman — one Indonesian and one Vietnamese — who had gotten ill, The Associated Press reported.

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

Police previously said the airport had not been decontaminated. Asked Friday in a text message whether that was still the case, Khalid said, “We are doing it now.”

Malaysian police had previously said no one besides Kim Jong Nam had been sickened during the airport attack.

If VX was used, it could have contaminated not only the airport but any place Kim had been, including medical facilities and the ambulance in which he was transported to the hospital. The nerve agent, which has the consistency of motor oil, can take days or even weeks to evaporate.

Some experts believe Iraqi dictator Saddam Hussein used VX against Iranians and Kurdish forces during the Iran-Iraq War in the 1980s. Japanese doomsday cult Aum Shinrikyo, which killed 12 people in a sarin gas attack in the Tokyo subway system in 1995, also used VX in a series of assassination attempts, killing one person.

North Korea says it doesn’t possess chemical weapons, but it is widely believed to have one of the world’s largest stockpiles. The South Korean Ministry of National Defense estimated in 2012 that North Korea had 2,500 to 5,000 metric tons of chemical weapons.

Read more:

VX nerve agent used on Kim Jong Nam: Just 10 milligrams on the skin can kill

North Korea breaks silence on Kim Jong Nam death, says probe 'full of holes'

Malaysia summons NK ambassador over Kim Jong Nam death

Police had said earlier that the two attackers rubbed a liquid on Kim Jong Nam's face before walking away and quickly washing their hands. He sought help from airport staff but died before he reached the hospital.

North Korea’s official, state-controlled media mentioned the case for the first time Thursday, saying Malaysia’s investigation was full of “holes and contradictions” without acknowledging the victim was Kim Jong Nam.

Long estranged from North Korea’s leadership, Kim Jong Nam had lived outside the country for years, staying in Macau, Singapore and Malaysia.

The two suspected attackers, and Indonesian woman and a Vietnamese woman, are in custody.

Contributing: Charles Ventura in Los Angeles