Debris from the blast in the town of Blankenburg flew up to 60 meters and some people were seriously hurt, police spokesman Uwe Becker told n-tv television.
Other people were being evacuated from the five-story block, which contains 60 apartments.
Becker said that he couldn’t rule out a gas explosion as the cause of the blast just before 9 a.m., and didn’t at present have any other likely explanation.
The building is on the edge of Blankenburg, a town of about 20,000 people in the Harz mountains, west of Berlin.
About 100 children at a nearby day care center were taken to other facilities.