Firefighters battled a two-alarm blaze in a residential building on Meridian Street in East Boston late Thursday night. A firefighter suffered a knee injury. The fire, which was first reported at 10:05 p.m., is believed to have started on the second floor of the three-story house, Boston fire officials said. The fire then spread to the third floor and roof. No injuries were reported, but nine adults and four children were displaced, said Fire Department spokesman Steve MacDonald. The property, at 358 Meridian St., suffered an estimated $250,000 in damages, he said.