Investigators believe someone intentionally started a large fire that burned several row homes under construction in Philadelphia.

A reward of $12,500 is being offered for information that leads to an arrest and conviction. The Bureau of Alcohol, Tobacco, Firearms and Explosives announced a $10,000 reward on Tuesday, and City Councilman Kenyatta Johnson added $2,500.

The fire was reported Monday morning in the city's Point Breeze section. About 75 firefighters battled the flames for an hour. One of the structures collapsed and several more were severely damaged. No one was hurt.

The developer told the Philadelphia Inquirer he plans to start rebuilding the destroyed homes and break ground on the project's second phase of development this week.—AP