A fast-moving fire at the Morgan Woods housing complex in the Ocean Heights area of Edgartown early Wednesday evening severely damaged two homes and left three families homeless.

Edgartown fire chief Peter Shemeth said the fire likely started when a small propane tank attached to a backyard grill behind 26A English Oak Circle, part of a three-unit complex, began to vent and caught fire. The blaze ignited the rear corner of the home and quickly spread to the adjacent unit.

The grill was being operated by Rebecca Searle, who lives at 26A English Oak Circle, although it is unclear if she left the grill unattended. Michael Cass lived in the middle unit, which sustained the heaviest damage, and Alisha Dunnebier lived in the third unit, which sustained minor damage. The homes in Morgan Woods, a town-owned affordable housing development that opened three years ago, are duplexes and triplexes.

Chief Shemeth said a 20-pound tank also attached to the grill automatically vented as part of a safety system to prevent an explosion. The venting made a booming sound, although there are no indications either tank exploded. Fueled by the burning propane, the flames quickly destroyed the exterior walls and made their way up toward the roof.

“Once that tank became vented it was essentially one big blowtorch. It was a dangerous situation,” the chief said.

Tekla Silva, who lives on Morgan Way, said she heard a large boom and looked outside and saw flames reaching up the back of the triplex on English Oak Circle. The flames were as high as the treeline, she said. She then ran outside, and saw Ms. Searle outside with a little boy. Then there was another boom, that sounded like something exploded. “It sort of shook the ground a little,” she said. “Later I found a piece of debris on my yard . . . it looked like it shot up into the air.”

Alyssa Cimeno, another resident of Morgan Way, also heard the boom. “I thought at first it was fireworks, for the Fourth of July. But then I saw the fire.”

Bobby Lucero, who lives down the street, said it was a chaotic scene.

“There were bright orange flames that went up past the trees. And there was an explosion. I ran up there and I saw the woman outside. It looked like everybody was outside and safe. But still it was scary.”

Chief Shemeth said approximately 50 firefighters responded, including a truck from the Chappy fire house that came over on the ferry. As part of a standing mutual aid agreement, firefighters and trucks from Oak Bluffs also assisted.

No one was hurt in the blaze, although firefighters rescued a pit bull from the middle unit and a kitten from one of the corner units. The dog bit one of the firefighters in the confusion before being pulled to safety.

When firefighters arrived the building was fully involved, with flames shooting through the roof of the center unit. The firefighters tried an interior attack, the chief said, but eventually pulled back because the flames were heading up toward the roof.

“It was heading into the attic so it could vent at the peak in the roof. We ended up coming in with [hoses from] the ladder truck and hitting it with hand lines from underneath,” he said.

Chief Shemeth said all the units are separated by fire walls, although the fire was able to spread through the roofs and attics. The fire was extinguished in under an hour, but hot spots continued to smolder for long afterwards.

The chief said most of the damage was confined to the roof and attics of the three units.

The roof in the middle unit was completely destroyed, while the roof in the first unit will need to replaced. He said the two corner units can likely be saved, and said there is hope the middle unit can also be rebuilt.

“Considering the circumstances, it could have been worse,” he said.

Jessica Burgoyne, site manager for Morgan Woods, said representatives from the Salvation Army and Red Cross have been on the scene to provide assistance to the three families who have been displaced by the fire.

“That’s why I love this community, people help each other out,” she said.

She said the three families have made arrangements to stay with friends and families in the short term, while various charitable organizations are helping to find lodging for them for the longer term. “I will say it’s a terrible situation. Right now we are here to meet the needs of our tenants as best we can . . . these families will need some help,” she said.