THOUSANDS are being warned to stay indoors and prepare to evacuate after a massive explosion from a German chemical factory lit up the night sky.

More than 14,000 people were urged to close the doors and windows of their homes in Ritterhude, near Bremen, shortly after the 8.30pm (Germany time) explosion sent thick billowing clouds of toxic fumes into the night sky.

Nach Explosion in Lackfabrik in #Ritterhude: Einsatzkräfte finden schwer verletzte Person: http://t.co/0naaEE7T6G pic.twitter.com/uRBZFSJVow — buten un binnen (@butenunbinnen) September 9, 2014

More than 300 firefighters are responding to the call.

At least one man has so far been rushed to hospital with third degree burns.

One employee has so far been reported as missing.

“We have so far only discovered his car,” police spokesman Mark Neumann told media.

The plant, which sits on the outskirts of Ritterhude, is believed to produce industrial paints and solvents.

picture of a hat Explosion in Bremen Germany 09.09.14 pic.twitter.com/HKQQk48aqT — Marco Wegener (@wegener0815) September 9, 2014

Local residents were initially warned to stay indoors as the thick black smoke filled the sky and to prepare for possible evacuation.

The Bild newspaper reports the local police as saying the explosion was heard “dozens” of kilometres away.

Picture of a hat Explosion in Bremen,09.09.14 pic.twitter.com/WahakMSHqh — Marco Wegener (@wegener0815) September 9, 2014

Radio Bremen reports several subsequent explosions have been heard since the initial blast sent shockwaves through local residents.

Fears remain high about the toxicity of the smoke and firefighters are being equipped with breathing apparatus.

The railway line between Bremmen and Bremerhaven has been closed.

Surrounding houses were reportedly damaged by the blast which has “severely damaged” buildings within the plant itself. A police officer has told media several structures - including houses - were in danger of collapse.

Up to 20 nearby residents have reportedly been treated for minor injuries and shock.