KUALA LUMPUR (Reuters) - Malaysian authorities said on Tuesday they had still to establish what was used to kill the estranged half-brother of North Korean leader Kim Jong Un, and the body had not been formally identified as no next of kin have come forward.

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Kim Jong Nam was killed at Kuala Lumpur International Airport on Feb. 13 with what police believe was a fast-acting poison. Malaysia’s deputy prime minister has previously named the victim as Kim Jong Nam, though authorities have been unable to conduct DNA tests.

“The cause of death and identity are still pending,” Dr Noor Hisham Abdullah, director general of health at Malaysia’s health ministry, told reporters.

The health ministry official said no DNA samples had been received from the next of kin.

South Korean and U.S. officials have said they believe North Korean agents assassinated Kim Jong Nam, who had been living in the Chinese territory of Macau under Beijing’s protection.

Malaysia has urged Kim Jong Nam’s next-of-kin to claim the body and help with the inquiry, which has sparked a diplomatic row with North Korea, whose officials want the body handed over directly.

Malaysia recalled its envoy from Pyongyang after North Korea’s ambassador in Kuala Lumpur cast doubt on the impartiality of Malaysia’s investigation and said the victim was not Kim Jong Nam.

North Korean ambassador Kang Chol said on Monday that his country “cannot trust” Malaysia’s handling of the probe into the killing.

Responding on Tuesday, Malaysian Prime Minister Najib Razak denounced the ambassador’s comments and reiterated that the investigation would be fair.

“The statement by the ambassador was totally uncalled for. It was diplomatically rude. But Malaysia will stand firm,” Najib told reporters.

Authorities have still to release an autopsy report.

But, the health ministry official said a post mortem examination carried out two days after the death found no evidence of a heart attack or of any puncture wounds on the body.

Malaysian police have arrested a North Korean suspect, and say that four other North Koreans fled the country later on the day of the attack.

Two women from Vietnam and Indonesia have also been arrested on suspicion of carrying out the assault on Kim Jong Nam. There is speculation that they administered a poison by wiping it or spraying it on his face.

Airport camera footage released on Monday by Japanese broadcaster Fuji TV shows the moment the women appeared to assault Kim Jong Nam, who is later seen asking airport officials for medical help.

Reuters could not independently verify the authenticity of that footage.