Chemical company BASF says two people are still missing after an explosion at its plant in the southwestern German city of Ludwigshafen that left at least two dead.

BASF said Tuesday that the fire at a river harbor in the sprawling facility was extinguished on Monday night, about 10 hours after the explosion. Two employees have been confirmed dead and another six people were seriously injured.

The explosion followed a fire in a pipeline between an area where liquids are unloaded from ships on the Rhine river and storage tanks. BASF said that the substances that burned in the subsequent blaze included ethylene — used in producing solvents and insulation — and propylene, used in producing car paint and adhesives.

It isn't yet clear what caused the blast.