1 of 4 A car and a house are destroyed after an explosion in Wuppertal, Germany, June 24, 2018. German police say 25 people were injured, when an explosion destroyed a several-store building in the western city of Wuppertal. (Henning Kaiser/dpa via AP)

1 of 4 A car and a house are destroyed after an explosion in Wuppertal, Germany, June 24, 2018. German police say 25 people were injured, when an explosion destroyed a several-store building in the western city of Wuppertal. (Henning Kaiser/dpa via AP)

BERLIN (AP) — Twenty-five people were injured, four of them severely, during an explosion that destroyed an apartment building in the western German city of Wuppertal, police said Sunday.

Police said the explosion produced a large bang and rocked the multi-story building shortly before midnight Saturday, frightening people nearby so badly they ran out into the streets.

The cause and nature of the explosion was under investigation, German news agency dpa reported. The blast had so much force it destroyed the attic and top three floors of the building, dpa said.

Fires broke out in several areas of the structure, while firefighters had trouble dousing the flames ceilings, walls and floors kept collapsing. They located four severely injured people in the wreckage who were hospitalized, according to dpa. Another 21 were treated at the scene for less serious injuries.

Emergency personnel on Sunday picked up bricks and furniture on the street. A car was destroyed, buried under window frames that were blown onto it by the explosions’ impact.

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Some of the building’s roof beams stood black and eerie in the smoke as police scoured accessible parts of the building for anyone who might trapped inside before giving the all-clear.

Where the building stood is now a huge gap in a row of apartment buildings in the city’s Langerfeld neighborhood.

Later Sunday, authorities brought in heavy equipment to tear down the remains of the ruin. They said it was too dangerous for investigators to search for evidence that might reveal the explosion’s cause because the destroyed building could collapse at any time.