Kim Jong-nam, the half-brother of North Korea's leader, was killed by a highly toxic nerve agent, says Malaysia.
Mr Kim died last week after two women accosted him briefly in a check-in hall at a Kuala Lumpur airport.
Malaysian toxicology reports indicate he was attacked using "VX nerve agent", which is classified as a weapon of mass destruction by the United Nations.
There is widespread suspicion that North Korea was responsible for the attack, which it fiercely denies.
It responded furiously to Malaysia's insistence on conducting a post-mortem examination and has accused Malaysia of having "sinister" purposes.
Malaysia's police chief Khalid Abu Bakar said on Friday that one of the women Mr Kim interacted with at the airport had also fallen ill with vomiting afterwards.
He said the airport and areas the suspects are known to have gone to would now be cleaned.
Mr Kim died on the way to hospital shortly after the 13 February airport encounter. His body remains in a hospital mortuary, amid a diplomatic dispute over who should claim it.
Mr Khalid said today, Friday, that the presence of the nerve agent was detected in swabs taken from Mr Kim's eyes and face by the Chemistry Department of Malaysia.
He said other exhibits were still under analysis and that police were investigating how the banned substance might have entered Malaysia.
"If the amount of the chemical brought in was small, it would be difficult for us to detect," Reuters quoted him as saying.
Bruce Bennett, a weapons expert at the research institute the Rand Corporation, told the BBC it would have taken only a tiny amount of the substance to kill Mr Kim.
It would have begun affecting his nervous system immediately, causing first shaking and then death within minutes.
Mr Khalid has previously said the fact the woman who accosted Mr Kim immediately went to wash her hands showed she was "very aware" that she was handling a toxin.VX nerve agent
The most potent of the known chemical warfare agents, it is a clear, amber-coloured, oily
liquid which is tasteless and odourless
Works by penetrating the skin and disrupting the transmission of nerve impulses - a drop on
the skin can kill in minutes. Low doses can cause eye pain, blurred vision, drowsiness
It can be disseminated in a spray or vapour when used as a chemical weapon, or used
to contaminate water, food, and agricultural products
VX can be absorbed into the body by inhalation, ingestion, skin contact, or eye contact
Clothing can carry VX for about 30 minutes after contact with the vapour, which can expose
Official chemical name is S-2 Diisoprophylaminoethyl methylphosphonothiolate and it is banned
by the 1993 Chemical Weapons Convention