Japan provided Malaysia with fingerprint data for Kim Jong Nam, the half brother of North Korean leader Kim Jong Un, to help with the investigation into his murder last month at Kuala Lumpur International Airport, according to sources close to the matter.

The data was obtained when immigration officials detained him in 2001 at Narita International Airport as he tried to enter the country on a false passport. He told the authorities he wanted to visit Tokyo Disneyland.

The disclosure marks the first time Japanese assistance has come to light in the investigation into the fatal poison attack, which is widely believed to have been orchestrated by North Korea.