What Is VX Nerve Agent? North Korea Says Kim Jong Nam Cause Of Death Wasn't Poison

North Korea denied allegations Thursday that Kim Jong Un’s estranged half-brother had been killed by a state-manufactured, deadly nerve poison. Despite a Malaysian autopsy that showed VX nerve poison had killed Kim Jong Nam, North Korean officials said the man died as a result of a heart attack.

Kim died Feb. 13 while waiting for a flight at Malaysia’s Kuala Lumpur International Airport. Two women were captured on surveillance video seemingly attacking him and subsequently charged with murder. North Korea told Malaysian officials not to perform an autopsy, but Malaysia went ahead with the procedure. The findings showed remnants of the deadly poison on his face and eyes.

North Korean officials, however, said the two women would have died or taken ill had they been in contact with a poison that deadly.

“This is a strong indication that the cause of death is a heart attack,” Ri Tong II, former North Korean ambassador to the United Nations, said in a press conference Thursday. He noted that Kim had suffered from heart disease, diabetes and high blood pressure.

VX was categorized as a chemical weapon and banned during the Chemical Weapons Convention in 1993. The lethal, amber-colored liquid is odorless and tasteless and extremely potent and toxic when it comes in contact with the skin or is inhaled. VX sends the body’s glands and muscles into a state of hyper-stimulation, quickly causing a person to enter a state of exhaustion and stop breathing. However, it is possible to prevent illness or death from exposure if the poison is immediately removed or treated, the Centers for Disease Control and Prevention noted.

Malaysian police dismissed the notion that Kim had died of a heart attack and noted that the two women would have known to wash their hands immediately and extensively following the attack, preventing their death or sickness.

Relations between Malaysia and North Korea have become increasingly tense in the wake of each country’s claims about the incident. Following Kim’s death, Malaysian officials said they had been looking into diplomatic relations between the two nations because of the use of a chemical weapon. Malaysia also halted visa-free travel to the country for North Korean travelers Thursday.