BERLIN - An explosion at an apartment building in the western German city of Wuppertal on Sunday (June 24) injured at least 25 people, four of them severely.

Several residents escaped after the blast, but others were trapped and had to be rescued by the fire brigade. A large number of rescuers were on the scene to free people from the block, reported German broadcaster Deutsche Welle.

Pictures from the scene showed piles of rubble around the multi-storey apartment block. The cause of the blast was not immediately clear and an investigation was under way.

"It can currently not be ruled out that there are still other people in the building," the police said. "The rescue efforts are ongoing."

Specialist engineers were called into stablise the partially collapsed building to prevent it from completely falling.