The Boston Fire Department says "careless disposal of smoking material" this morning sparked a two-alarm fire that displaced 12 people and injured a firefighter at 24 Freeman St.

The fire, right behind the inbound platform at the Fields Corner Red Line stop, was reported around 10:15 a.m. It started under the 2 1/2-story building's rear porch.

One firefighter suffered burns. The department estimated damage at $300,000.