Story highlights North Korean suspects did not hold diplomatic passports

Indonesian suspect says she thought she was on a prank show

Kuala Lumpur (CNN) Malaysian police are looking for four more suspects, all of them North Korean, in connection with the mysterious death of Kim Jong Nam, the estranged half brother of North Korean leader Kim Jong Un.

Authorities said they are treating the incident as a murder case.

Top police official Noor Rashid Ibrahim addressed reporters in Kuala Lumpur on Sunday. When asked whether Malaysian authorities thought Kim's death had been ordered by the North Korean regime, he said only that "the four hold North Korean nationality, that is all."

Ibrahim said the suspects do not not hold diplomatic passports.

Kim Jong Nam was on his way to catch a flight Monday morning to see his family in Macau when he died. Police say he was sprayed with poison as he waited to board the flight at Kuala Lumpur International Airport.