Images shared on social media showed a huge smoke cloud rising into the sky. The Federal Office for Civil Protection and Disaster Assistance (BBK) warned the public to close their windows and to stay inside amid fears of dangerous leaked gasses. A tank with solvents is reportedly still on fire. One person tweeted they felt their house shake in Bergisch Gladbach, which is around seven miles away from Leverkusen.
The warning app, Nina, urged people in the district of Bürrig to go inside and close all doors and windows.
It said: "Explosion in Bürrig, warning level: extreme danger
"Close your doors and windows, go inside buildings, only call 112 if you have information on the events."
They urged people to listen to the local radio station and avoid the affected area.
According to local reports, the first indication is that the explosion happened at a garbage incineration plant in Bürrig.
The fire brigade also asked for help to keep the emergency number free.
A large cloud of black smoke can also be seen from Cologne - which is around 18km away from Leverkusen.
According to the Cologne fire brigade, there is currently no danger in the city area.
The Cologne fire brigade tweeted: " The @Feuerwehr_Koeln (fire brigade Cologne) is currently in a support mission for the @Feuerwehr_Lev (Fire brigade Leverkusen).
"A large column of smoke on the site of a waste incineration plant can be seen from afar.
"The responsibility lies with the fire brigade / City of Leverkusen."
The local radio station Radio Leverkusen says it happened at around 9.30am local time.
READ MORE: M11 traffic: Motorway finally reopens hours after horrific lorry fire
But they said they cannot send reporters to the scene as they do not know if some "dangerous substances" may have been leaked.
They said: "Currently it is still not clear what kind of gasses might have escaped, we will keep you updated."
Soot particles are reportedly falling from the sky.
The radio station reported: "By now we know that an overhead wire was torn off, which is why the police faced issues getting to it at the beginning.
DON'T MISS
Tesco 'explosion' terrifies locals as major supermarket evacuated [INSIGHT]
Dubai explosion horror: ‘Oil tanker’ engulfed by huge flames [REVEAL]
Caspian Sea explosion: Huge fireball sighted off coast of Azerbaijan [COMMENT]
"It seems that there are several severely injured and several burn victims and it hasn't been confirmed yet but there are also said to be two or three dead people."
They also warned people to remember to turn off their air conditioning systems.
North Rhine-Westphalian police confirmed there have been several people injured.
They tweeted: "The situation in #Leverkusen -Wiesdorf is currently still unclear.
"We are on-site with many police officers and clarify the situation.
"There are several injured."
According to FOCUS-Online information, the employees of the Chempark are currently not allowed to leave the site for safety reasons, and a power failure is expected for the rest of the day.
The huge explosion could be felt all the way to Bonn - around 41km away from Leverkusen.
According to Western German Broadcaster, witnesses said the large column of smoke can be seen rising over the premises of the Bayer chemical company and can be seen for miles.
A disposal facility in the plant is believed to have been affected.
The smoke is reportedly moving towards Lützenkirchen, Opladen and Rheindorf and parts of Cologne now stink "abominably".
The press office of the Chemapark in Leverkusen has since confirmed that an explosion had occurred.
Chemapark tweeted: "For a currently unknown cause, there was an explosion in the Chempark Leverkusen.
"Plant fire brigade and air test vehicle at the scene.
"Residents please go inside closed rooms and keep doors and windows closed."
More than 5,000 chemicals are manufactured in the Chempark, including nitriding and chlorination products, aromatics, fine chemicals and silicon chemistry.
Additional reporting by Monika Pallenberg
More to follow...