Indian police on Saturday questioned the mother of 15-year-old Scarlett Keeling raped and murdered in Goa last month, saying it was routine questioning to clarify some aspects of the case.

Fiona MacKeown, who has accused authorities of trying to cover up the murder, was questioned after receiving a summons on Friday night.

Indian authorities had originally said Keeling's death was an accident, but later arrested two people after a second autopsy revealed she could have been killed.

MacKeown's lawyer Vikram Varma said the initial summons given to the mother appeared to relate to whether she was negligent in leaving her daughter in Goa. Facing media criticism, the police had backed down from this line of questioning, he said.

MacKeown left her daughter in the care of friends in Goa while she went on travelling in southern India.

"The questions were soft and not related to negligence," Varma said.

The Indian media and lawyers have criticised police for failing in the past to properly investigate murder cases.

MacKeown has written to the Indian Prime Minister Manmohan Singh seeking his intervention, as she feels the case has weakened, with the police sitting on vital medical tests for weeks to confirm the presence of drugs in Keeling's body.

The autopsy revealed bruises all over Keeling's body, that her mouth was stuffed with sand and she did not have enough saltwater in her lungs to indicate drowning.

Keeling's case is the latest to highlight the safety of tourists in India. Tourism officials met this year to discuss attacks on tourists after at least seven foreign women and girls said they had been raped or molested.