The body of Kim Jong-nam has been targeted in a morgue break-in.
Heavily-armed special forces were deployed to the Malaysian hospital on Tuesday and have remained in place since.
Malaysian police say they know who orchestrated the attempted break-in, but wouldn't provide a name.
"We knew there were attempts by someone to break into the hospital mortuary," police chief Tan Sri Khalid Abu Bakar told the Malay Mail.
"We had to take precautions. We will not allow anyone to tamper with the mortuary."
Jong-nam, the brother of North Korean leader Kim Jong-un, was attacked at an airport in Kuala Lumpar. He died on the way to the hospital.
CCTV footage appears to show a female hit squad place a cloth over his face. The footage then shows Jong-nam, 46, speaking to authorities, gesturing to his face.
Malaysian police confirmed the victim had complained to airport personnel that two women had "wiped his face with liquid".
Two women and two men have been arrested in connection to the attack - nationals from Vietnam, Indonesia and North Korea.
Siti Aisyah, the 25-year-old Indonesian suspect, thought she was taking part in a TV prank, according to Indonesian authorities. Her boyfriend has also been arrested, along with a 28-year-old Vietnamese woman and a 47-year-old North Korean man.
Police are seeking three more North Koreans, including Kim Uk Il, who works for North Korea's national airline Air Koryo. They are also seeking Hyon Kwang Song, who works at the North Korean embassy in Kuala Lumpur and another North Korean, Ri Ju U.
Four additional North Koreans previously sought by Malaysian police are believed to have fled to Pyongyang.
Malaysia is one of North Korea's few allies, but the incident has raised diplomatic tensions between the nations.
North Korea is strongly denying claims that the women wiped a toxin on Jong-nam, and they have angrily objected to an autopsy being carried out. The embassy in Kuala Lumpur is calling for the immediate release of the "innocent females" who were arrested.