BERLIN — An explosion at a chemical park shook the German city of Leverkusen on Tuesday, sending a large black cloud rising into the air.

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.

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