Two people died and 31 were injured in an industrial park explosion that shook the German city of Leverkusen on Tuesday. Several people are missing.
Emergency services took three hours to extinguish the fire at the Chempark site, home to chemicals companies Bayer and Lanxess. It started after the blast at 9:40am (07:40 GMT), park operator Currenta said.
"My thoughts are with the injured and with loved ones," said Chempark chief Lars Friedrich. "We are still searching for the missing people, but hopes of finding them alive are fading."
Police said five of the 31 injured needed treatment in intensive care.
"This is a tragic moment for the city of Leverkusen," said Uwe Richrath, mayor of the city, which lies north of Cologne.
The area and surrounding roads were sealed off for much of the day.
Police told residents living nearby to stay indoors and to shut doors and windows against any toxic fumes.
Currenta said air conditioning systems should be switched off while it measured the air around the site for toxic gases.
Mr Friedrich said it was not clear what caused the explosion, which led to a fire in a tank containing solvents.
"Solvents were burnt during the incident, and we do not know precisely what substances were released," he said.
"We are examining this with authorities, taking samples."
Sirens and emergency alerts on the German civil protection agency's mobile phone app warned of "extreme danger".
Leverkusen is less than 50 kilometres from a region that was hit last week by catastrophic floods that killed at least 180 people.
More than 30 companies operate at the Chempark site in Leverkusen, including Covestro, Bayer, Lanxess and Arlanxeo, according to its website.