THE HAGUE, Netherlands (AP) — Dutch police say four children have been killed and two people seriously injured in a collision between a train and a cargo bike.

The accident Thursday morning happened on a railway line in the town of Oss 100 kilometers (62 miles) southeast of Amsterdam.

Further details were not immediately available about the cause of the accident. Dutch media report that it happened at a railway crossing.

Cargo bikes, which have a large wooden box mounted to the frame in front of the rider, were formerly used for transporting goods but are now very popular among Dutch parents for carrying young children.