Malaysian police have said that the terminals at the Kuala Lumpur International Airport are devoid of any hazardous substances after they swept through the facility over the murder of Kim Jong-nam, the estranged half-brother of North Korean leader Kim Jong-un.

The authorities said they have not found toxic chemicals at the airport, where Kim was assassinated using the VX nerve agent – a material declared by the UN as a weapon of mass destruction.

"The joint operations, carried out by the police forensic team, AELB and Fire and Rescue Department Hazmat unit started around 1.45am and ended about an hour later," said police chief, Abdul Samah Mat. "Based on our screenings, we have come to three conclusions that there are no hazardous materials detected, KLIA2 is free from any form of contamination and the airport is declared a safe zone."

The sweeping operations were carried out as a precautionary measure to look for any lingering traces of the powerful chemical agent. So far, none of the people who helped Kim shortly after the assault have shown any effects of the chemical substance. Tens of thousands of travellers have passed through the airport ever since the high-profile incident and none of them have reported any after-effects.

"We decided to go ahead with the screening at 1.45am as there would be fewer people in the airport and we did not want to cause any unnecessary alarm. Those who attended to the victim after the attack have also undergone examination and they are all okay."

Kim was attacked at the airport on 13 February by two female assassins, purportedly acting under the orders of the North Korean regime. He was declared dead while en route to the hospital and later forensic tests revealed the substance was a nerve agent causing him serious paralysis.