ORONO, Maine — The fire that claimed the lives of two brothers early Sunday morning started in the home’s damaged chimney, and fire officials on Monday urged Mainers to check their smoke detectors and heating systems to help prevent further deadly blazes.

State Fire Marshal Joseph Thomas said Sunday’s fire at 53 Hillside Road, which was first reported around 3:20 a.m., originated in the unlined chimney after a spark set off debris that accumulated in gaps left by missing bricks and crumbling mortar.

“The inside of the chimney was in pretty rough shape,” Thomas said Monday morning.

In the wake of the fire, investigators found one body on the second floor and another in the first-floor living room. They later identified the victims as Randy Davis, 47, who owned the home, and his brother Cris “Cricket” Davis, 49. No working smoke detectors were in the home, according to Thomas.

A third man, who investigators feared also might have been in the home because his vehicle was parked in the driveway, was found safely at his residence in Bangor. Police and fire officials declined to identify him.

The three men had been out drinking Saturday night and took a cab home. After dropping the brothers off in Orono, the cab continued to Bangor, where it dropped off the friend, according to Maine Department of Public Safety spokesman Stephen McCausland.

On Christmas Eve, a Boston Red Sox baseball cap hung from a branch in front of the home, over the yellow police tape. The hat was meant to serve as a makeshift memorial, with the words “Randy and Cris, We miss you! Love, The Rucks, Lowell, Leah, Deanna and Phil” and several hearts drawn on the brim.

Since the fire, neighbors have said Randy and Cris Davis were amiable people who always waved when passing by or stopped in the yard for small talk. The brothers both worked as crossing guards in Orono.

Randy Davis, who was well known in the community, shepherded children across Main Street at the crosswalk near the fire and police stations.

Orono fire Lt. Bryan Hardison lives a few doors down from the home on Hillside Road.

“He walked his dog in the neighborhood,” Hardison said of Randy. “I’d see him every day.”

Randy Davis often stopped to chat with neighbors during the four or more walks he took his golden retriever on daily. Hardison said Randy’s dog also died in the fire.

Hardison said he and Davis talked about “anything and everything — how things had been going, what was going on in town.” In one of their more recent conversations, they talked about how Christmas shopping was progressing, according to Hardison.

“He was the kind of neighbor that you like to have,” Hardison said.

David Cox, neighbor of the brothers, said the lights from the firetrucks woke him up early Sunday morning. He said he saw smoke pouring out of the windows “like liquid, just black.”

He said Randy Davis enjoyed having get-togethers in his backyard during the summer, playing horseshoes and chatting around a fire pit.

On Sunday, after firefighters had put out the blaze, Cox said he and his partner went around their building, including the upstairs apartments, to check each of the smoke detectors and make sure they were in working order.

Kory Tibbetts, former general manager of Curva Ultra Lounge in Orono, said Cris Davis worked there as a cook for about three years before he left the business last year. The club closed in September. Tibbetts said Cris was a father of two.

Tibbetts said the brothers were “financially strapped” but “always so positive.”

“They were both genuinely great guys,” Tibbetts said, adding that they spent a lot of time together.

Cris Davis was a huge fan of the Philadelphia Flyers and rock music, especially his son’s band, according to Tibbetts.

“All I can think about is [Cris’] two kids,” Tibbetts said. “And worse, his father, who just lost two kids.”

Autopsies to confirm the victims’ identities and causes of death were scheduled to begin Monday, but the results likely will not be ready for release until Wednesday, Mark Belserene of the state medical examiner’s office said Monday morning.

Fire officials on Monday stressed the importance of having multiple working smoke detectors in homes and checking the condition of chimneys, especially when using a stove to burn wood, pellets or other fuel.

“Anybody that is using an alternative heating appliance on an unlined chimney should at least have it looked at by a certified chimney sweep,” Thomas said.

Hardison said many fire departments, if requested, will come to homes to inspect chimneys or stoves for compliance.

Officials also warn people to keep combustibles, such as cardboard and paper, away from stoves, pipes or other pieces of heating systems.

An Orrington father and his three children died Nov. 9 when fire swept their home, after cardboard stored too close to the stove caught fire. Investigators said there were no working smoke detectors at that home either.

There have been 19 fire fatalities in Maine in 2012, according to Thomas.

On Dec. 20, 1989, another Orono fire claimed the lives of three siblings — Michael Nickels, 16, Brian Nickels, 6, and Laurie Nickels, 4 — while their mother was at a friend’s home in Old Town wrapping Christmas presents. A fourth child, David, then 11, escaped the burning building by jumping out of a second-story window, according to Bangor Daily News archives.

“It’s always a tragedy, but this time of year just makes it harder for everybody,” Hardison said.

Tibbetts said he “envied” the Davis brothers and their positive outlook on life.

“These two had more happiness in their lives than people who have everything,” he said.