ST. GEORGE, N.B. -- The four family members who died in a house fire this week in St. George, N.B., were all killed by smoke inhalation, fire officials confirmed Thursday.

The provincial fire marshal's office said the blaze was not considered suspicious in nature, but the exact cause remained undetermined as it closed its investigation.

"We're satisfied, based upon our dialogue with the fire marshal's office, that there is not a criminal component to this fire." RCMP Sgt. Chris Henderson said in an interview. "(Fire officials) don't necessarily have to determine the specific cause of the fire for us to be satisfied that it wasn't intentionally set ... It is 100 per cent non-criminal in nature."

Still, the fire marshal's office issued a statement asking members of the public to come forward if they had any information about what happened inside the home.

The fire on South Street was reported shortly after noon, and the four occupants of the old house -- 80-year-old Esther Boyd and her adult sons Davey, Billy and Robbie -- were later pronounced dead at the scene. The three men were in their 50s and were believed to have mental challenges.

"This is a very tragic event and the community is absolutely in shock," said Henderson. "Four wonderful people are deceased."

According to the family's obituary, Esther and her sons had lived in St. George for most of their lives.

"Esther ...devoted her life to her family and the church," the obituary said.

Davey Boyd was an honorary member of the St. George fire department. He was well known in the community of 1,500 in southwestern New Brunswick, about 120 kilometres south of Fredericton.

Neighbours say Davey Boyd could often be seen walking around town dressed in a formal firefighter's uniform. He was also known to take part in local parades, and he worked at the firehall, where he cleaned the trucks.

Sterling Harris, a town councillor, said Davey Boyd had been visiting the local fire hall Tuesday morning to see a new fire truck, then headed home at around noon shortly before the fire.

On the Facebook page for the Town of St. George, the fire department has posted a photo of a fire truck with "David B. Boyd" painted on a front visor. Said one commenter: "I can see that big smile now. He would have been so happy."

A private family service is planned for Saturday at the St. George Rural Cemetery. A memorial service will be held at the St. George Baptist Church later in the day.