The explosion happened in a part of the site where waste is incinerated, a spokesperson for Currenta said. Chempark, an industrial park for the chemicals industry, said on Twitter it was not yet clear what caused the explosion, Euronews reported.
“Residents should please go indoors and keep doors and windows closed,” Chempark said.
The German government’s civil protection agency warned of “extreme danger”.
Broadcaster WDR had earlier cited witnesses as saying they had heard an explosion and that they saw plumes of smoke at chemicals maker Bayer’s site.
Police said on Twitter that it was closing a nearby motorway.
Bayer and chemicals firm Lanxess in 2019 sold Chempark operator Currenta to Macquarie Infrastructure and Real Assets for an enterprise value of 3.5 billion euros ($4.12 billion).
($1 = 0.8492 euros)
RHM/PR