Mounties say a house fire that put three people in hospital Sunday, including two young children, is believed to be suspicious.

The two-alarm blaze broke out in the basement suite of a home on 144B Street at around 10:30 a.m., triggering a massive emergency response in the neighbourhood involving eight ambulances.

Witnesses watched as firefighters and paramedics performed first aid on the victims, including young children they described as a baby and a toddler.

"Firemen gave them CPR," said Ragender Chauhan, who lives in the area. "We all pray for them."

On Monday, Surrey RCMP confirmed both of the children remained in critical condition.

"They are in hospital receiving treatment and investigators are monitoring their condition," Const. Richard Wright said.

The third victim, an adult, has already been released from hospital.

Despite labelling the fire as suspicious, police stopped short of saying it was deliberately set. Wright said investigators are still working with Surrey firefighters to determine where and how the fire started.

The family living in the basement of the home had only been there a few months. Neighbours told CTV News police have been to the home before, and were last seen at the property hours before the fire started.

Mounties confirmed they visited the home on Sunday, but would not say why, or whether it could be related to the fire.

With files from CTV Vancouver's Nafeesa Karim

Correction: The RCMP has confirmed the adult victim was not released from hospital, but transported to a different hospital. He remained in critical condition as of July 12.