Three bodies have been pulled from a burning home in Nanaimo, B.C., according to first responders.

The victims include two adults and a seven-year-old girl, according to RCMP, and the serious crime unit is investigating.

A bystander called to report the fire in the 700 block of Nicol Street shortly after noon on Tuesday, and firefighters discovered the bodies as they tried to bring the flames under control, said Fire Chief Karen Fry.

The chief wasn't able to speculate about the cause of the fire.

"It's hard to say at this point in time. The house is set back from the road enough that the fire could have been going for quite some time before anyone noticed," she told CBC News.

The coroners service has also been called in to investigate, and Fry said a thorough probe would begin Wednesday morning, after the site has cooled down.

She described the fire as stubborn and said firefighters were still working at the scene two and a half hours after the blaze was first reported.

"These type of incidents are not only traumatic for the individuals and their families but our staff and all the responders as well. It's very difficult to deal with," Fry said.

She added that it's not clear if there were working smoke alarms in the home. Officials have not released any identifying information about the three dead people.

With files from Liz McArthur and the Canadian Press