The cause of a fatal fire at a rental house in Boothbay on Sunday was a child playing with matches, according to the state Fire Marshal’s Office.

Department of Public Safety spokesman Stephen McCausland said in a statement that the blaze started when the first-floor living room couch caught fire and quickly spread through the two-story house.

Baldomero “Bart” Zamora, 50, and Lucas Farias, 23, died in the early-morning fire. Julie Gilbert, 48, who survived by jumping out a second-floor window, was Farias’ mother.

Zamora and Farias apparently tried to escape, and their bodies were found near windows in two upstairs bedrooms.

No criminal charges will be filed, given the child’s age, the Fire Marshal’s Ooffice said. The child will be referred to counseling.

Gilbert, Zamora and Farias were from Chicago, although Gilbert formerly lived in Damariscotta.

Also in the house were Alexandra King, 26, and 8-year-old Harley Raymond and 4-year-old River Raymond, of Winslow. They were treated and released from a local hospital, McCausland said.

Investigators say the house was equipped with three working smoke detectors.

Firefighters said the blaze was so intense that they couldn’t get inside the house, which was built in 1935.

The owners of the house had listed it on the online rental site Airbnb and it had been rented through the Columbus Day holiday.

Art Dunlap, a code enforcement officer for Boothbay, said the town doesn’t regulate Airbnb rentals, nor does it have any special rules for homes that are rented out on short-term arrangements.

Investigators said survivors of the fire told them the house had been rented for a belated birthday party for Zamora, who turned 50 last month.

Family members said they were told by fire officials that Zamora knew he would die when he broke open a second-floor window to save Gilbert – but the stairway leading downstairs had already collapsed.

Elva Zamora, Baldomero Zamora’s sister, said Sunday that she talked to the lead investigator of the fire and he said that, based on what he saw and a statement by Gilbert, the couple was trapped upstairs because the stairway had collapsed and “their only option was the window.”

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