Rescue teams in western Germany are continuing to search for five missing workers at an industrial park for chemical companies where an explosion killed at least two people and injured 31 others, according to reports.

The explosion at the waste management facility of the Chempark site in the city of Leverkusen, near Cologne, on Tuesday produced a blaze that took firefighters almost four hours to extinguish.

The chief executive of Currenta, which operates the Chempark industrial park, said there was little hope for the five missing workers — four Currenta employees and one outside contractor.

A dark cloud of smoke rises above the Chempark in Leverkusen
A dark cloud of smoke rises above the Chempark site in Leverkusen (Oliver Berg/dpa via AP)

“We have to assume that the missing people can no longer be found alive,” Frank Hyldmar said.

He added that of the 31 injured, one person remained in a life-threatening condition.

Police said that investigations into the cause of the explosion would begin on Thursday, German news agency dpa reported.

It appears the blast may have been linked to storage tanks filled with solvents.

A police officer blocks an access road to the Chempark site
A police officer blocks an access road to the Chempark site (Oliver Berg/dpa via AP)

Residents were asked to stay indoors and several major roads were closed for hours after the explosion sent a large black cloud into the air.

City officials also warned people not to let children play outside, use outside pools, or eat fruit and vegetables from their gardens over the coming days.

Leverkusen is home to Bayer, one of Germany’s largest chemical companies and one of the biggest employers in the region. The city has about 163,000 residents, many of whom work for Bayer.

The industrial park is located close to the banks of the river Rhine.