An autopsy on a 13-year-old foster child who died in hospital after being found in distress at a friend's home Friday morning has failed to reveal a cause of death. RCMP say the autopsy did not reveal an injury and no natural cause was found.

Police did say the Medical Examiner's office will continue their investigation with toxicology results, which could take up to five months to complete.

Stony Plain RCMP confirmed to media Monday, a witness had observed the 13-year-old male voluntarily ingest something, but police have not identified what that is.

RCMP reported they were called to a home in Stony Plain at the request of Alberta Health Services around 9 a.m. Friday. Police arrived to find a 13-year-old male who appeared to be in distress.

"I don't believe it was the foster home," said Const. Barbara Roy. "I believe he was having a sleepover with friends when he became distressed."

The boy was taken to Stony Plain Hospital where he was later pronounced dead. 

The teen cannot be identified under provincial law. The youth's biological father tells CTV News he was in shock when he heard about the death of his son. The man says he's had limited contact with the boy since he entered the foster care system six years ago.

"He was so smart, so funny," said the man.

The boy's family says he and his older brother had been living in the same foster home for close to a decade. A home the family describes as a loving and positive environment.

Along with the RCMP, the province is also investigating the events leading up to the boy's death.

"From our perspective what we do in a case like this is we would also review our file to ensure the supports and services provided to the young person were appropriate," said Trevor Coulombe, spokesperson for Alberta's Children and Youth Services.

The boy is the third foster child to die in Alberta in the past year.

The Alberta Liberals said the recent deaths have them very concerned about the system and are calling on the government to launch a public inquiry into the boy's death.

The Paul First Nation, where the boy once lived, is planning a private ceremony for the family Tuesday night. A funeral is being planned for Wednesday.

With files from Scott Roberts