KYODO Kyodo / Reuters Kim Jong Nam arrives at Beijing airport in Beijing, China, in this photo taken by Kyodo February 11, 2007.

KUALA LUMPUR (Reuters) - VX, the chemical used in the airport murder Kim Jong Nam, is one of the deadliest chemical weapons created by man. Just 10 milligrams of the nerve agent or a single drop enough to kill in minutes, experts say.

With the texture and feel of engine oil, VX was first produced in the United Kingdom in the 1950s. It can cause convulsions, loss of consciousness, paralysis and respiratory failure in minutes.

Its only known use is as a chemical warfare agent: VX is classified as a weapon of mass destruction by the United Nations.

“You can think of VX as being a pesticide on steroids, this is an extraordinarily toxic substance. Roughly 1/100th of a gram, a third of a drop, on someone’s skin, will kill them,” said Bruce Bennet, defense researcher at California-based RAND Corporation.

Malaysian police said on Friday that VX was found on the body of Kim Jong Nam, the estranged half-brother of North Korean leader Kim Jong UN, and they are investigating how the chemical entered the country.

VX and other nerve agents were believed to have been used in chemical warfare during the Iran-Iraq War in the 1980s. In 2015, traces of VX and sarin - another nerve agent - were found at a military research site in Syria that had not been declared to the global chemical weapons watchdog.

HARD TO PRODUCE

Sarin gas was used in Syria, killing hundreds in deadly attacks in 2013, and by members of a Japanese doomsday cult in their deadly 1995 attack on a Tokyo subway.

But VX is known to be much more potent than sarin and other nerve agents because of its persistency. Sarin evaporates from the skin surface but VX does not.

The chemical is hard to produce but a few countries are known to make it and remain in possession of it. The United States and Russia still have some VX stockpile.

South Korean analysts have identified sarin and VX as the focus of a North Korean chemical weapons program. Pyongyang has denied that.

Symptoms after contact with VX in vapor form will appear within a few seconds, and within a few minutes to up to 18 hours after exposure to the liquid form, said John Allum of forensic science firm Hawkins.

VX is considered to be much more toxic by entry through the skin and somewhat more toxic by inhalation. Any visible VX liquid contact on the skin, unless washed off immediately, is believed to be lethal, according to the U.S. government’s Centers for Disease Control and Prevention.

BARE HANDS

People may not even know they have been exposed to VX as it is tasteless and odorless. In fact, it is unlikely to have been detected by airport security or sensors if it had been brought in small amounts.

Kim Jong Nam was murdered at the main Kuala Lumpur airport last Monday while he was waiting in the departure hall to take a flight to Macau, where he was known to be living with his family for years under Chinese protection.

He had spoken out publicly against his family’s dynastic control of the isolated, nuclear-armed state. South Korean and U.S. officials say North Korean leader Kim Jong Un likely ordered the assassination of his half brother.

North Korea unsuccessfully tried to prevent an autopsy on the body, accusing Malaysia of working with South Korean and other “hostile forces.” Pyongyang has said Malaysia should be held responsible for killing one of its citizens, though it has not acknowledged the victim is Kim Jong Un’s half-brother.

Malaysian police say two women are believed to have attacked Kim Jong Nam, using their bare hands to wipe his face with a liquid. The women were then instructed to wash their hands off afterwards.

The two women and a North Korean have been detained in Kuala Lumpur. Police are searching for seven other North Koreans, four of whom are believed to have fled to Pyongyang.