Yvonne Fritz, Alberta's minister of child and youth services, says she ordered an investigation into the case of a foster child who died Wednesday as soon as the toddler arrived in hospital. (CBC)The death of an Alberta toddler who was in foster care is being investigated as a homicide, RCMP said Thursday.

The 21-month-old girl, from the Morinville area, died Wednesday after being brought to an Edmonton hospital in serious condition on Monday. An autopsy was performed Thursday morning but the cause of the girl's death has not been released.

Neighbours said that they saw paramedics rush the girl out of the house on a stretcher while pumping her chest at about 4 p.m. Monday. Sources told CBC News that the toddler likely succumbed to injuries caused by shaken baby syndrome.

CBC News also learned Thursday that the child was in the care of two foster families before she died.

The child had been cared for by members of one foster family but they needed a break, so she was put in the care of another foster family to provide some respite care. CBC News also learned the child was recently in the care of a driver who was to take her for a visit with her biological mother, though that visit never occurred.

"This is a very tragic situation, and it's very heartbreaking," Yvonne Fritz, the Alberta minister of child and youth services, said of the toddler's death.

Ministry to investigate

The ministry will conduct its own investigation concurrent with the police investigation.

"This investigation will be very thorough," Fritz said. "It began when this child was hospitalized … it used to be that we did a case review following the police investigation, which could be a year at times or longer, and this investigation that I've directed is immediate."

The minister said she expects the results of her department's investigation within eight to 10 weeks and will follow through on any recommendations in that report "immediately."

Alberta child welfare legislation means the child, her parents and her foster parents cannot be identified.

'A terribly difficult time for everybody'

"I think that this is a terribly difficult time for everybody — for caseworkers, for foster parents, for everybody," said John Mould, Alberta's Child and Youth Advocate. "One can't have anything but just incredible sadness for what's happened."

Mould said he will be part of the investigation into the circumstances of the little girl's life and how she died.

"Every one of these situations is important and it needs to be looked at and understood. We need to learn as much as we possibly can from each one of these instances," he said.

"But it is also important that we don't lose the perspective that there are lots of young people and lots of foster homes out there where things are working well."

The Alberta New Democratic Party has been calling for a public inquiry into the child welfare system for more than a year, said party leader Brian Mason. He said the province failed the foster child by ignoring that call.

"Vulnerable children are at risk, the government knows it, and their response has been to cut $26 million from the services that prevent tragedies like this from happening," Mason said in a release.

In last month's provincial budget, the Children and Youth Services Department's budget was cut by $36 million, with most of that coming from child intervention services.