A four-alarm fire in a vacant north Philadelphia warehouse left a firefighter injured after a fall and disrupted public transit, authorities said.

The blaze in the four-story building in the Fishtown section of the city was reported at about 2:30 a.m. The flames burned out of control for almost two hours before fire officials pronounced the blaze under control, but crews were still pouring water on the smoking ruins well after daybreak.

The blaze happened near the Southeastern Pennsylvania Transportation Authority's Market-Frankford Elevated Line, forcing service to be halted and replaced with shuttle buses between two stops. Commuters were warned to expect delays and crowded conditions through the morning. SEPTA said late Tuesday afternoon that it had resumed full service on the line.

The Philadelphia Inquirer said one firefighter was taken to Hahnemann University Hospital, where he was reported in stable condition.

Fire Commissioner Lloyd Ayers said no evacuations were ordered but some nearby residents left their homes on their own. The cause of the fire was under investigation.