A devastating fire at a home in Oshawa has claimed the lives of a man, woman, and two children, officials confirmed Monday.

The fire broke out at a residence on Centre Street North, near Colborne Street, shortly after 8 a.m.

Speaking to reporters Monday morning, Oshawa Fire Chief Derrick Clark said emergency officials received multiple reports of people trapped on the upper floors of the home.

When firefighters arrived on scene, they discovered heavy smoke and flames coming from the house. Clark said firefighters were surrounded by flames “at all times” as they made their way to the upper level and initially had to retreat. He said crews were able to access the second floor on a second attempt.

“Oshawa Fire Services crews did an extraordinary, valiant, and brave job trying to get up to the upper levels. They knocked the fire down from the outside, knowing that there were reports of people trapped, made entry, and made their way up to the upper levels of the house,” Clark said.

“We had severe fire conditions that worsened and we evacuated all personnel from the building, made a defensive attack, and then regrouped and went back in for search and rescue.”

A man, woman, boy, and girl were pulled from the home but were later pronounced dead. Clark said two victims were located on the upper floors of the two-storey house and one on the main floor. The fourth, one of the children, was pulled from the home but later died in hospital.

The victims have not yet been formally identified by authorities. However, two friends identified the woman as Lindsey Bonchek and said two of Bonckek's children -- Jaxon and Maddie -- died in the fire as well. A fourth person, identified as Steven MacDonald, was also killed.

Friends say Bonchek’s third child, a 16-year-old, was at school when the fire broke out.

An estimated 11 people lived in the multi-unit home and three other tenants were taken to hospital for treatment. Their condition is not known.

"It's very sad," said a nearby store owner, who identified himself as John. "The little girl was just here three days before, she bought a mug. I feel so sad for her."

One neighbour said she heard someone screaming, “My baby, where’s my baby?” as they ran out of the burning home.

“They were all just running around,” the neighbour, who did not provide her name, said. “The gentleman, Steven, he ran back into the house to try and control the fire, which was already out of control. He then ran back in to get one of the children, as far as I know.”

A GoFundMe page set up for the family indicates that a seven-month pregnant woman was able to escape the home without injury.

“However, her father Steven MacDonald passed away while courageously running back into the building to save the others,” the online fundraising effort reads.

The cause and origin of the fire has not yet been determined and the Office of the Fire Marshal will be called in to assist in the investigation.

It is not yet known if smoke detectors were functioning in the home at the time of the fire.

“There were reports that firefighters initially did hear some alarms but I can’t confirm that nor can I confirm what location of the house they were coming from,” Clark said.

Clark said the weather conditions created a challenging situation for emergency responders.

“This fire was at the height of the snow storm this morning. Very difficult conditions both for crews driving on route here as well as fighting this fire,” he said.

Clark went on to offer condolences to the families involved.

“This is a tragic event,” he said. “These are the types of events that we want to eliminate in the future and Oshawa Fire Services is committed at doing that.”

Oshawa Mayor John Henry said when a fire results in a loss of life, it is always “upsetting” to the community.

“We’ve had some major industrial fires over the years but in my recollection, this would be one of the worst events we’ve had in a long time,” he said.

“To the families, we pass on our deepest sympathies to you.”

Investigators with Oshawa Fire Services and the Ontario Fire Marshal expect to be at the home investigating the cause of the fire for several days.