Mahmoud al-Mabhouh was found dead in a hotel room in Dubai
A Hamas commander who was killed in his Dubai hotel room was drugged and then suffocated, according to results of forensic tests released by police.
Mahmoud al-Mabhouh's killers used a quick-acting muscle relaxant to help make the death seem "natural", a senior Dubai police officer said.
Israel's secret service has been widely blamed for the killing.
However Israel has said there is no evidence it was behind the killing on 20 January.
It has accused Mabhouh of smuggling arms into Gaza and killing two Israeli soldiers.
"The killers used the drug succinylcholine to sedate Mabhouh before they suffocated him," Maj Gen Khamis Mattar al-Mazeina, deputy commander of Dubai's police, said.
"The assassins used this method so that it would seem that his death was natural," AFP news agency quoted him as saying.
Succinylcholine is a rapid onset muscle paralysing agent, which has no sedative properties. Medics say that a person injected with the drug would eventually suffocate because his muscles are entirely paralysed.
Some previous reports on Mabhouh's death have suggested he was electrocuted and suffocated.
Dubai has identified 26 suspects in the murder and said they used British, Irish, French and Australian passports.
The use of the European and Australian passports in the assassination has sparked a diplomatic row between those countries and Israel.
The countries say the passports used by the murder suspects were forged.
British police officers are in Israel to investigate the use of fake British passports by some of the suspects.
Israeli officials have refused to either confirm or deny their country's involvement in the killing but have hailed it.
Trade Minister Binyamin Ben-Eliezer said on Sunday he did not know who had carried it out, but it showed Hamas that "none of their people are untouchable".