Malaysian officials trying to determine whether poison killed the half brother of North Korea's leader in a busy airport have said post-mortem tests are so far inconclusive.
More than a week has passed since Kim Jong Nam was approached by two women at a budget airline terminal in Kuala Lumpur and apparently sprayed in the face with an unknown substance.
He did not suffer a heart attack and had no puncture wounds, such as those a needle would have left, according to Noor Hisham Abdullah, director general of health, but he did not dismiss poison as a potential cause.
He added that medical specimens have been sent to experts for analysis.
The case has perplexed leading forensic toxicologists who study murder by poison. They say the airport attack is one of the most bizarre cases in the books, and question how the two women could walk away unscathed after deploying an agent potent enough to kill Mr Kim before he could make it to hospital.
Some type of nerve gas or ricin, a deadly substance found in castor beans, have been suggested as possible toxins used.
A strong opioid compound could also have been liquidised, although that would probably have incapacitated the victim immediately. Surveillance footage shows Mr Kim walking calmly downstairs to the airport's clinic.
The older half brother of North Korea's reclusive ruler Kim Jong Un had spent most of the past 15 years living in China and south-east Asia. He is believed to have had at least three children with two women, but no family members have come forward to claim the body.
The attack spiralled into diplomatic fury when Malaysia refused to hand over the body to North Korean diplomats and proceeded with a post-mortem over the ambassador's objections.
The two nations have made a series of increasingly angry statements since then, with Malaysia insisting it is simply following legal protocols, and North Korea accusing Malaysia of working in collusion with its enemy South Korea.
Seoul's spy agency believes North Korea was behind the killing, but has produced no evidence.
Malaysian prime minister Najib Razak told reporters on Tuesday that the North Korean ambassador's remarks were "diplomatically rude" and said Pyongyang "should help us to find out the truth".
Police have so far arrested four people carrying identity documents from North Korea, Malaysia, Indonesia and Vietnam. They include two women who were allegedly seen approaching Mr Kim on February 13 as he stood in the departure hall at an airport ticketing kiosk.
One of the women, Doan Thi Huong, is from Nghia Binh, Vietnam, a largely Catholic farming village about 80 miles south of Hanoi. Her father, Doan Van Thanh, said he cannot believe she would do such an "earthshaking" thing.
"She is my daughter and I understand her," he said. "She was scared of rats and toads. She would not have dared to do such thing."
Mr Thanh said his daughter left the village about 10 years ago to study at a pharmaceutical school in Hanoi, and once told him she was working in communications.
The Indonesian woman who was arrested has said she was tricked into taking part in the attack, believing it was part of a comedy TV show stunt.
Grainy video from airport security cameras obtained by Japan's Fuji TV seems to show two women approaching Mr Kim from different directions, with one slipping up behind him and appearing to hold something over his mouth for a few seconds.
Then the women turn and calmly walk off in different directions.