A bus carrying about 60 passengers crashed on the A44 highway in the western German state of North Rhine-Westphalia, injuring more than 20 people, police said on Thursday night.

The bus veered off the road and overturned on its side near the town of Werl, 100 kilometers (60 miles) east of Düsseldorf.

A 20-kilometer stretch of the A44 autobahn from the Unna Ost exit to Werl in the direction of Kassel was completely closed.

Firefighters and a rescue helicopter were dispatched to the scene.

What do we know about the crash?

Police initially said 21 people were lightly injured and one was seriously injured. They later revised the number to 20 lightly injured and one seriously injured.

A police spokesman said the bus was carrying students from a vocational school in Warburg. They were returning from a trip to England.

The cause of the accident was still unclear. Police said no one’s life was in danger and no other vehicles were involved in the accident.

The accident came just a day after four people were killed in a bus crash near Leipzig in eastern Germany.

This report was written in part with material from news agency DPA.

Edited by: John Silk