Neighbors watch as police investigate the Blackstone Street house where three bodies were found.

PROVIDENCE — The police yesterday discovered the bodies of three people, an adult couple and the woman’s teenage son, who died under unexplained circumstances in a house in South Providence.

Although the police initially treated the case as a homicide, Deputy Police Chief Paul J. Kennedy said last night that a preliminary autopsy found no evidence of trauma to the victims and that the deaths may have been accidental.

Kennedy disclosed at a community meeting that a boiler recently had been installed in the single-family house, at 345 Blackstone St. A preliminary investigation, the police added later, showed that its installation was faulty and that there was an elevated level of carbon monoxide present.

The police withheld the identities of the victims but said the bodies were those of a man, a woman and a young male.

However, a neighbor and a friend identified two of the occupants of the house as Sonia Maritza Flores, 46, also known as Sonia Maritza Aleman, and her son Ryan, 16, a student at the Met School. The neighbor, Jasmin Osorio, 25, said Flores’ longtime boyfriend lived with them.

Another neighbor called the police at 12:14 p.m., after a relative of Flores’ called neighbors and asked for help in contacting his family, according to Kennedy. Osorio identified the relative as an older son of Flores’ who serves in the Navy and is stationed in the South.

The neighbor could get no response when he checked, so the police were called.

Officers found “a bad scene” inside, said Kennedy, who added later that the victims had been lying there “for a period of time.” When detectives, wearing masks, gloves and paper booties over their shoes, opened the doors and windows to air out the house, an offensive odor permeated the vicinity.

The police said a city inspector and a representative of the gas utility company National Grid made a preliminary inspection of the house and its heating system and came to a preliminary conclusion that the system had been installed improperly.

The police intended to keep the scene secure overnight, and they said a further inspection of the mechanical system was expected to be done today.

The state medical examiner’s office is working to conclusively determine the victims’ identities and their cause of death.

Mayor David N. Cicilline, Police Chief Dean M. Esserman and Kennedy conducted a community meeting at Davey Lopes Recreation Center on nearby Dudley Street to address public concerns about the incident.

“We hope to have answers within a day or two,” Kennedy told an audience of about 20 adults and a half-dozen children. “There’s nothing right now that says we’re looking at a homicide or a violent death.”

Esserman said the police would be on the streets all night and at the dead teen’s school today in an effort to allay the fears of residents and to make them feel safe.

“We have lost three people,” the chief said. “How, we don’t know yet.”

When the police arrived at the house, they found three decomposed bodies. Esserman said that whenever there is a death, “and we’re suspicious,” the matter is treated as an apparent homicide. That was the information disseminated widely by the news media for most of the day.

Early yesterday afternoon, as children down the street walked home from school, staff from the state medical examiners office were removing the white-wrapped bodies from the front door. Some neighbors, one with a baby in her arms, watched in silence as the gurneys were loaded into two white trucks.

The police Bureau of Criminal Identification van, which serves as a base for criminalists who lift fingerprints and collect other forensic evidence, was parked at the curb of the narrow street. Within an hour of the police having been called, detectives began canvassing neighbors in their houses, and a perimeter of yellow crime-scene tape was expanded to keep neighbors and newspeople at bay.

The neatly kept green-painted clapboard house, surrounded by a chainlink fence, has decorative scallop-shaped maroon and green shingles near the peaked roof and cream trim. Faded Christmas tree stickers are still in the first-floor windows. A wad of mail filled the mailbox beside the front door.

Blackstone Street is on the rebound from a sad decline, with a number of houses having been built in the past decade. Next door to 345 Blackstone and across the street are two daycare centers.

Blackstone is one block away from the Lockwood neighborhood, where the Providence police worked with the community to rid the area of street-level drug dealers. Lt. George Stamatakos, commander of the local police district, said the last major complaint from Blackstone residents was about children who had knocked down a fence and were cutting through from Comstock Street. The police and one of the landlords had the fence repaired.

“This is a really nice, quiet street,” Stamatakos said.

The mayor, who came to the scene, called the incident a “terrible tragedy for the city.”

Shortly after 5 p.m., an animal control officer arrived and carried out a cage that contained a dead gray rabbit. The caged pet had been located in the basement.

Richard Daluz, a teenager from the neighborhood, said that his longtime friend, Ryan Aleman, 14, lives in the house and that they are students at the Met School.

Richard said he sent a text message to Ryan on New Year’s Eve, but did not hear back. Then, Richard said, he knocked on the door last Thursday, looking for Ryan. The porch light was on, Richard said, but no one responded.

“I had a feeling something had happened,” he said.

tbreton@projo.com