LUDWIGSHAFEN: Several people were injured and some were missing on Monday after blasts at two German chemicals plants owned by BASF which forced the world's biggest chemicals company to shut down some production facilities.

BASF said there was an explosion and a fire broke during work on pipelines in the north harbor area of its Ludwigshafen site, where it is headquartered, at around 11:30 local time (5:30 am ET).

Several people were injured and some are still missing, it said in a statement. It is investigating the cause of the explosion and is shutting down its two steam crackers, large facilities that make important basic chemical components, as well as some other units.

The city of Ludwigshafen advised residents in the surrounding area to avoid going outside and to keep their windows and doors shut.

The Ludwigshafen site, around 80 kilometers (50 miles) south of Frankfurt, is the world's largest chemical complex, covering an area of 10 square kilometers (4 square miles) and employing 39,000 workers, according to BASF.

Images published by local media showed flames and a plume of thick black smoke at the site's harbor, a terminal for combustible fluids such as naphtha and methanol that are important for BASF's supply of raw materials.

Separately, four people were injured in an earlier gas explosion at BASF's Lampertheim facility.

BASF said it was also still investigating the cause of that explosion, which occurred at 08:30 local time. It has switched off the Lampertheim facility, which makes additives for plastics.