Two employees at BASF, the world's largest chemical company have died in a fire and explosion at its Ludwigshafen site on Monday (17 October). Six people were critically injured and two are still missing, said the company in a statement.

An explosion belched out plumes of smoke, causing BASF to turn off some of its production facilities. A fire spread quickly following the blast, with the company warning residents of Ludwigshafen to keep doors shut and to stay indoors.

Emergency crews fought to contain the inferno triggered by the blast, and firemen were among the missing, according to a Telegraph report.

"We deeply regret that employees died and several people were injured. Our sympathy is with the affected people and their families," the Ludwigshafen site's chief, Uwe Liebelt, said in a statement.

It remains unknown at present what triggered the blast and BASF said it could not comment what financial impact the explosion could have.

The company has shut down 14 facilities, including its two steam crackers, which are large units that make basic chemical components. This was for safety reasons. In addition, the supply of raw materials was disrupted by the blast. The place where the blast took place is a terminal for combustible fluids such as naphtha and methanol.

"We will of course do everything we can to clear the matter up," site chief Liebelt said, reports Reuters.

The Ludwigshafen site is nearly 80 km (50 miles) south of Frankfurt, and the world's biggest chemical complex, covering an area of 10 square kilometres (four square miles). Around 39,000 employees are based here, according to BASF.

Two hours before news of the explosion broke, BASF said four people were hurt in a gas explosion at its Lampertheim site that makes additives for plastics.

The fire was still smouldering by Monday evening but believed to be under control, a local fire department spokesman said. The incident was filmed and posted on Twitter, saying that the explosion caused a "giant column of fire."