What we know about VX nerve agent that allegedly killed Kim Jong Nam The fast-acting poison was used in the apparent assassination of Kim Jong Nam.

 -- The fast-acting poison used in the apparent assassination of Kim Jong Nam at a crowded airport terminal in Malaysia last week was the banned chemical weapon VX nerve agent, according to police. Kim Jong Nam is the estranged half-brother of North Korean leader Kim Jong Un.

The Royal Malaysia Police said in a statement today that a preliminary analysis found VX nerve agent on the eyes and face of the victim, who was allegedly attacked in a departure area of the Kuala Lumpur International Airport and died as he was being transported to the hospital on Feb. 13. The man was carrying North Korean travel documents bearing the name Kim Chol with a birth date of June 1970 and birthplace of Pyongyang, the capital of North Korea.

Malaysian police officially use the passport identity, Kim Chol, and have requested DNA from family members to confirm the man’s identity. But Malaysian Deputy Prime Minister Ahmad Zahid Hamidi told reporters last week that the North Korean embassy in Malaysia had confirmed the man was Kim Jong Nam, the eldest sibling of Kim Jong Un who has been living overseas for years, according to The Associated Press.

The South Korean Unification Ministry also said at a press briefing last week that it recognized the victim was “certainly Kim Jong Nam.”

Malaysian police have arrested four people in connection with the attack and said they are searching for additional suspects.

Inspector-general of police, Khalid Abu Bakar, told reporters on Wednesday the two women suspected of fatally poisoning the man were trained to coat their hands with toxic substances and wipe them on his face. Khalid said the women knew what they were doing and had practiced the attack multiple times.

"We strongly believe it is a planned thing and that they have been trained to do that. This is not just like shooting a movie," he told reporters, according to The AP.

Here’s what is known about the deadly toxin that allegedly killed Kim Jong Nam.

What is VX?

VX is a man-made chemical warfare agent that’s classified as a nerve agent, the most toxic and quick-acting of the known chemical warfare agents. Nerve agents are similar to pesticides in terms of how they work and the noxious effects, but they are much more potent, according to the Centers for Disease Control and Prevention.

VX is an oily liquid that is odorless, tasteless and amber in color. It has the consistency of motor oil and evaporates very slowly, according to the CDC.

The aging half-life for VX is about 48 hours, making it the slowest aging nerve agent, according to the ABC News Medical Unit.

Where is it found?

VX was first produced in the United Kingdom in the early 1950s, according to the CDC.

The nerve agent is banned under the Chemical Weapons Convention, an international treaty which North Korea never signed. Instead, the isolated nation has spent decades developing a complex chemical weapons program that has long worried its neighbors and the international community.

How does it work?

Like all nerve agents, VX unleashes its toxic effects by preventing the proper operation of an enzyme that acts as the body’s “off switch” for glands and muscles. Without this “off switch,” the glands and muscles are stimulated relentlessly. They may tire and no longer be able to sustain breathing function, according to the CDC.

VX enters the body through the skin or inhalation. Its works fastest if inhaled through the lungs, according to the ABC News Medical Unit.

Symptoms will appear within seconds of exposure to the vapor form of VX; for the liquid form, it could take minutes or hours for symptoms to show. Even a tiny amount of this nerve agent can be lethal, according to the CDC.

What are the symptoms?

Symptoms of VX exposure include blurred vision, confusion, cough, diarrhea, drooling, drowsiness, eye pain, excessive sweating, headache, increased urination, nausea, rapid breathing, runny nose, vomiting, watery eyes and weakness. These symptoms could last for hours after exposure, depending on the amount.

A victim exposed to a large dose of VX may also experience convulsions, loss of consciousness, paralysis or respiratory failure possibly leading to death.

Victims exposed to a small or moderate dose of VX usually recover completely. Those who are severely exposed are not likely to survive, according to the CDC.

Death usually occurs within 15 minutes after absorption of a fatal dose of VX, according to the ABC News Medical Unit.

Is there treatment?

Recovery from VX exposure is possible with treatment, which consists of removing the deadly toxin from the body as soon as possible and providing medical care in a hospital setting. An antidote can be administered by injection but it must be used quickly to be effective, according to the CDC.

"It's a very toxic nerve agent. Very, very toxic," Dr. Bruce Goldberger, a leading toxicologist who heads the forensic medicine division at the University of Florida, told the AP. "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."

ABC News’ Joohee Cho, Conor Finnegan, Benjamin Gittleson, Matt Gutman, Joshua Hoyos, Maureen Jeyasooriar, Luis Martinez, Gillian Mohney and Joseph Simonetti contributed to this report. The Associated Press also contributed to this report.The Associated Press also contributed to this report.