A fire that heavily damaged an Onset home on Wednesday, April 3, was determined to be accidental.

"The most probable cause," said Onset Fire Capt. Howard Andersen, is "careless disposal of a cigarette.”

The fire started just after 3 p.m. on the back porch of the single-family, two-story home at 6 Storer Street.

The couple who lives at the home got out OK.

A firefighter sustained a minor injury during the incident, and was transported to Tobey Hospital, fire officials said. The firefighter was treated and released.

A neighbor who identified herself as Michelle said that she noticed a lot of smoke, and then saw that there was fire in the back of the home.

"I spotted it and told my neighbor to call 911," she said. "I walked out back and the porch was on fire. ... Then, it just took off."

Firefighters first at the scene "found heavy fire conditions on the rear deck, rapidly extending to the house and an adjacent garage," fire officials said. "After the heavy fire was knocked down, the crews continued to work, overhauling and wetting down hot spots, until the fire was extinguished.

Crews reported that the fire was mostly out just after 4 p.m. A total of 40 firefighters were at the scene.

The Wareham Fire Department assisted at the scene and with staffing Onset Fire's station in the village. The Bourne and Marion fire departments also provided assistance. Wareham EMS was at the scene.

Wareham Week will update this story when more information becomes available.