Chemical weapons experts are "mystified" over reports that a nerve gas was used to murder Kim Jong-nam, the estranged half-brother of North Korean leader Kim Jong-un, according to a New Scientist article.
Malaysian investigators insist Kim was poisoned using VX by two women at Kuala Lumpur International Airport on February 13, and died en route to the hospital.
"I have more questions than answers at this point," the science magazine quoted Richard Guthrie, formerly of the Stockholm International Peace Research Institute, as saying.
New Scientist explained that the nerve agent VX is the most toxic substance known, saying "10 milligrammes of the oily liquid on your skin, less than a drop, is lethal."
Similar symptoms but slow reaction
"But Kim took some time to show any symptoms, while the poison was handled by unprotected assailants, and didn't contaminate other people," the magazine said.
"The attacker was handling a cloth with no apparent protection, not wielding a syringe. The women are then said to have run to a washroom to wash their hands, where one vomited. Both are consistent with VX," the article said.
"But nothing else seems to have happened to them, even though they were apprehended soon after."
"Any splash of a tiny droplet anywhere on her body would have resulted in some symptoms," the magazine quoted chemical weapons expert Jean-Pascal Zanders as saying.
The article suggested that the attackers might have been pre-treated with atropine, a drug that blocks the effects of VX.
"But the medical staff who handled Kim in the ambulance where he later died – with convulsions, which is consistent with VX but also other poisons – would not have been pre-treated," it said.
If it was VX, the airport concourse should have been decontaminated, Zanders told the magazine.
Who dun it using what?
Zander told the magazine that samples from Kim's remains should be sent to a lab certified by the Organisation for the Prohibition of Chemical Weapons which enforces the chemical weapons treaty. There is one in neighbouring Singapore.
South Korean and US officials have said the killing was probably carried out by North Korean agents at the behest of Kim Jong-un. North Korea says the dead man is no relation to Kim Jong-un. The case has escalated diplomatic tensions between North Korea and Malaysia as the countries traded barbs over Malaysia's handling of the investigation.
Malaysian police have identified a total of eight North Koreans as suspects or as wanted for questioning. These include a North Korean embassy official believed to still be in Kuala Lumpur.
"Among eight suspects in this case, four are from the ministry of state security and two who actually took action are from the foreign ministry," Lee Cheol-woo, a South Korean lawmaker briefed by South Korean intelligence, said on Monday.