BERLIN, Dec. 13 (Xinhua) -- An explosion hit an apartment building in the German city of Blankenburg on Friday morning, injuring at least 25 people, according to local media Focus Online.

The blast happened in an apartment in the suburban area of the city and started a fire in the building. A nearby kindergarten was evacuated.

The cause of the explosion is still unclear.

More injuries have not been ruled out, police spokesman Uwe Becker said.

Three emergency helicopters were seen hovering over the site.