The half-brother of North Korean leader Kim Jong-un died last week after apparently being poisoned while waiting for a flight at a Kuala Lumpur airport.
There has been growing speculation that his son, Kim Han-sol, has travelled to Malaysia to claim the body.
Malaysia says the cause of death remains unknown.
Laboratory test results are still being awaited, the country's health ministry says.
The post-mortem examination showed no evidence of a heart attack and no puncture wounds were found on Mr Kim's body, director general of health Dr Hisham Abdullah told reporters.
The case has caused a diplomatic row between North Korea and Malaysia, which has refused to hand over the remains and conducted the post-mortem examination despite North Korean objections.
Security is high at the mortuary in Kuala Lumpur holding the body of Kim Jong-nam.
In the early hours of Tuesday morning, heavily armed police arrived at Hospital Kuala Lumpur followed by several unmarked vehicles.
There has been no official confirmation that Kim Han-sol is in Malaysia, but there is widespread speculation in Malaysian media that he arrived in the country on Monday night, from Macau.
The family of Kim Jong-nam have maintained a low profile life since falling out of favour with the North Korean regime.
Malaysia wants a member of the Kim family to provide a DNA sample so his identity can be confirmed before the body is released.
Dr Abdullah said that the North Korean embassy had not provided dental or medical records to assist with identifying the body. Malaysian officials have previously identified the dead man as Kim Jong-nam.
Meanwhile, harsh words continue to be traded between Malaysia and North Korea.
Malaysia has said it is "insulted" by comments from North Korea's ambassador, Kang Chol, who accused Kuala Lumpur of a cover-up.
"It has been seven days since the incident but there is no clear evidence on the cause of the death and at the moment we cannot trust the investigation by the Malaysian police," he told reporters.
"It only increases the doubt that there is someone else's hand behind the investigation."
Malaysia's Foreign Minister Anifah Aman said the diplomat's allegations were based on "delusions, lies and half-truths", while Prime Minister Najib Razak said they were "diplomatically rude".
Mr Kang has been summoned to explain his comments.
Malaysia has also recalled its ambassador to Pyongyang, Mohamad Nizan Mohamad, over the killing.
So far, four people have been arrested in connection with the killing - identified as being from North Korea, Malaysia, Indonesia and Vietnam - and at least four North Koreans are being sought by investigators.
Despite widespread speculation that North Korea was behind the killing, there has been no definitive evidence and Pyongyang is yet to issue an official statement.
South Korea has accused the North of orchestrating the incident, saying on Monday it was evidence of North Korean "terrorism getting bolder".
Malaysian authorities are yet to formally identify the body of Kim Jong-nam as no family member has come forward, officials say.