PORTLAND – Three people fled through a third-floor window to escape from an apartment house fire that drew hundreds of onlookers Tuesday evening and generated a plume of smoke that could be seen around the city.

Witnesses said they saw one resident, 31-year-old Matthew Meservey, hang a sheet out the window and then watched Meservey, his girlfriend and her son take turns making their way down the sheet partway to the ground before jumping to safety.

“There were like 15, 20 people out there trying to catch the little kid,” said Shaine Warren, 17, of Portland.

Warren and Justin Ramsey, 19, of Portland said neighbors tried unsuccessfully to break through the building’s front door.

Ramsey said a person in the crowd caught the child, identified by a family member as 10-year-old Zachary Towne. A group of men held up a mattress to break the fall of the boy’s mother, Josie Towne, 31, he said.

“All I was doing was praying for her,” said Charles Fortin, 61, of Portland, who said he was one of several men who held the mattress while others urged the nervous woman to jump.

Melanie Campbell, 32, Josie Towne’s sister, said Meservey and the boy were taken to Maine Medical Center with minor injuries. Josie Towne was still at the hospital Tuesday night with broken bones, Campbell said.

It took firefighters more than an hour to extinguish the fire, which spread through the walls and was difficult to fight, said Deputy Fire Chief Bill Flynn.

He said at one point crews were ordered out of the building “for their own safety.”

At least 15 people lived in the apartment complex. Most were not at home at the time of the fire, and others escaped through broken windows, the Portland Press Herald reported.

The building’s manager, Smith Phanoid, said the fire began when a propane tank for a grill exploded. Phanoid said it started on a porch that served as a fire escape for the third-floor apartment, blocking one exit route.

Investigators were looking into whether the east Bayside apartment complex had working smoke detectors and adequate exits at the time of the blaze, which began around 6 p.m. and gutted the building.