Explosion at chemical complex in German city of Leverkusen

An explosion at an industrial park for chemical companies has shaken the German city of Leverkusen, sending a large black cloud rising into the air

An explosion at an industrial park for chemical companies shook the German city of Leverkusen on Tuesday, sending a large black cloud rising into the air.

Germany’s Federal Office for Civil Protection and Disaster Assistance classified the explosion as “an extreme threat” and asked residents to stay inside and keep windows and doors closed, German news agency dpa reported.

Operators of the Chempark site in Leverkusen, about 20 kilometers (13 miles) north of Cologne on the Rhine river, said the cause of the explosion was unclear.

They said on Twitter that firefighters and pollution detection vans had been deployed.

Police could not immediately be reached for further details.

Daily Koelner Stadt-Anzeiger reported that the explosion took place in the Buerrig neigbborhood at a garbage incineration plant of the chemical park.

The paper said several nearby major highways had been shut down by police. It also reported that the smoke cloud was moving in a northwestern direction toward the towns of Burscheid and Leichlingen.

Leverkusen is home to Bayer one of Germany's biggest chemical companies.