PORT COLBORNE, Ont. -- Fire officials say four members of one family, including two children, have died in a house fire.

Fire Chief Thomas Cartwright says that before Wednesday's deadly blaze, the city of Port Colborne had only seen four fire-related deaths in more than four decades.

He says firefighters and the community are grappling to come to terms with the tragedy.

A neighbour, Adrienne Gerry, says she ran across the street as flames and heavy smoke engulfed her friends' home and watched emergency responders try to revive a woman.

She says two other family members, including the children's father, managed to escape and told her a mother and her two children, aged 2 and 15, remained inside the burning home.

Firefighters were called to the two-storey home in the Lake Erie community, south of Welland, Ont., around 1:20 a.m.

Niagara Regional police Const. Phil Gavin said emergency responders removed an 83-year-old woman from the home, but rescuers could not save that person's life.

He said a two-year-old boy, a 15-year-old girl and a 37-year-old woman remain unaccounted for, but are believed to be inside the home.

Gerry is close friends with the family and said she visits them daily. She said the victims include a woman, her two children and her grandmother.

She said the children's father and their great-uncle were able to escape.

The children's father "was out in a pair of boxers," she said. "My husband gave him all these clothes."

She said the children and their parents lived in a unit in the back of the house while the woman's uncle and grandmother lived in the front.

By Wednesday morning the fire had been extinguished, but the home remained unsafe to enter, Gavin said.

"Right now, the entire roof has collapsed into the residence and it burned for a little while so it's certainly a concern whether it's safe to put people in there," he said.

Gavin said it was too early to determine the cause of the fire, adding that the Ontario Fire Marshal's office is on scene investigating as well as the coroner.

Gerry said she is crushed at the overwhelming loss.

"I've never cried so much in my entire life," she said. "I haven't slept, I haven't done anything."

There will be no more trips to the beach with the children, she said. And no more gifts to shower upon the two-year-old boy.

Gerry's daughters, aged 8 and 10, were excited for Christmas because they adored the little boy.

"We got him a cute little outfit," Gerry said, crying. "Now, I don't know what we'll do. It just breaks my heart that he's not going to be around anymore."