The post mortem was carried out on the victims of the Wellawatte triple murder today, the police media unit said.
A special medical team appointed by court assisted in the post mortem and samples were also sent to the government analyst.
Once a report is obtained from the government analyst the cause of death will be determined, the police media unit said.
The police also said that they are still looking for the son of the parents whose bodies were found at the house in Wellawatte.
The bodies of the man, his wife and daughter were found on Saturday at a house down Ramakrishna road in Wellawatte.
Investigations revealed that they had come to stay there on rent but the boy had subsequently gone missing.
A court today issued an order preventing the suspect from going overseas in the event he attempts to flee the country.