A blast followed by a fire hit a chemical industrial park in the western German city of Leverkusen Tuesday, leaving two dead and dozens injured.

"We are deeply saddened by this tragic accident and the death of an employee," Chempark site operator Currenta said in a statement.

Currenta said the explosion occurred at a tank farm that is part of its facility and that the fire had been put out.

It added that a search was underway for several missing employees. Thirty-one others were injured in the blast, four of them seriously. 

"We hope that we can rescue the missing people alive," said Lars Friedrich, the head of Chempark, in an initial statement.

However, later in the day that tone had changed, when Friedrich released another statement announcing: "The search for the missing people is running at high pressure. Unfortunately, hope is disappearing that we will find them alive."

Bayer, one of Germany's largest chemical manufacturers, is headquartered in Leverkusen. The city of around 163,000 residents lies 20 kilometers (12.4 miles) north of Cologne.

What are local officials saying about the Chempark explosion?

Authorities warned residents not to consume food from their gardens and to beware of any film that may have settled on outdoor furniture, toys or in swimming pools.

Chempark urged people in Leverkusen to "go indoors and keep doors and windows closed."

Officials as far away as Dortmund, approximately 75 kilometers to the northeast of Leverkusen, advised residents there to do likewise.

"This is a tragic moment for the city of Leverkusen," said the city's mayor, Uwe Richrath.

What could have caused the explosion?

The Kölner Stadt-Anzeiger newspaper reported the incident occurred when three tanks containing organic solvents caught fire at a garbage incineration plant.

Residents said the blast could be heard from some distance, with some reporting that the force of the explosion had rattled their windows. 

It is unclear what caused the blast and whether toxic gasses were released during the accident. 

Daniel Dietrich, who heads a working group on human and environmental toxicology within the biology department at the University of Constance in southern Germany, told DW: "The images [of white smoke] suggest an explosive deflagration took place. As a result of an apparent fire and ensuing extinguishing operations — and the inherent drop in temperatures that these bring — the incomplete incineration of solvents stored in the tanks, for instance chlorinated compounds, will have led to the creation of byproducts."

"It is shocking to hear that employees were killed and seriously injured: My thoughts are with their families."

What is the Chempark?

With an overall surface area of 11 square kilometers (4.24 square miles), Chempark is one of the largest chemical sites in Europe. In 2019, German chemical giants Bayer and Lanxess sold a 60% stake in park operator Currenta to funds managed by Macquarie Infrastructure and Real Assets (Mira), which is owned by Australian investment bank and financial services company Macquarie Group. 

Chempark is made up of three different sites situated near the German towns of in Leverkusen, Dormagen and Krefeld-Uerdingen. According to Currenta, more than €1 billion ($1.18 billion) have been invested in the three locations over the last five years, so that it now boasts an "impressive vertical and horizontal range of production." 

More than 48,000 people from 50 countries work at the three sites in over 70 companies. Core companies like Bayer and Lanxess resident in Chempark can draw on the experience of 1,000 professional service firms in areas such as production management, research and logistics. The park's road infrastructure alone is about 100 kilometers long.  

Chempark's portfolio extends from the production of basic and fine chemicals through to the manufacture and processing of polymers, active ingredients and other chemical products. A total of 10,000 different chemicals are being produced here, with the chemical site connected to pan-European pipeline systems for naphtha, natural gas, ethylene and other petrochemical products. 

Henrik Böhme contributed to this report

ar,js/rt (Reuters, AP)