STRASBOURG, France (Reuters) – An explosion at a grain storage facility in the eastern French city of Strasbourg seriously injured three people on Wednesday morning, emergency services said.

It was not immediately clear what caused the blast, which set ablaze the silo located on the banks of the river Rhine, on the border with Germany.

The site is owned by agricultural cooperative Comptoir agricole. Local grain brokers said it had a storage capacity of 40,000 tonnes.

Comptoir agricole declined to comment.

France is the European Union’s largest grains producer and exporter. The Rhine serves an important route for transporting grain from eastern France to northern European countries like Germany and the Netherlands.

(Reporting by Gilbert Reilhac in Strasbourg, additional reporting by Valerie Parent in Paris, Writing by Gus Trompiz; Editing by Richard Lough)