An explosion at a German chemical plant killed one person Saturday and left another injured, rescuers and industrial park administrators said.

The explosion of a tank at the Evonik Degussa plant in the western town of Marl sent black smoke billowing over the town, and residents were warned to stay indoors, with their windows and doors closed.

The injured man was flown to a hospital, but officials later said his life was no longer in danger. A third person suffered only light injuries and had already left hospital.

Police later said that two employees who had been reported missing were found to be at their homes.

The substance contained in the tank is used in the production of plastic parts in the auto industry, as well as in cosmetics and electronics, an industry spokesman told AFP.

"Firemen have the blaze under control," a police spokesman said.

"A column of smoke rose 100 metres (320 feet) high in the wake of the explosion, but initial checks by environmental authorities don't indicate there's any danger to health," the spokesman added.

The cloud spread south towards the centre of town but was rapidly dispersed by the wind, he added.

The cause of the blast was not immediately known.

Marl, a town of 87,000 in the Ruhr industrial heartland, some 40 kilometres (25 miles) from Dortmund, is a key chemical industry centre.