MADRID --  At least 21 people were injured, two in serious conditions, after a train derailed in southern Spain on Wednesday, emergency services confirmed.

The accident happened shortly after 10:00 am local time when the third coach of a medium-distance train, travelling between Malaga and Sevilla, came off the rails between the stations of El Sorbito and Arahal in the province of Sevilla.

The exact cause of the accident is not yet known, but it happened in a 6 km stretch of track, which had previously been closed to rail traffic as the result of heavy overnight rain in the area.

Photos of the scene published in the Spanish press seem to show part of the ballast underneath the tracks had been washed away, with a section of rail partly covered by flood water.

Floodwaters and mud complicated the work of emergency services that were alerted to the incident at 10:12 am by a call from one of the 79 passengers on the train. In some cases emergency services were only able to arrive after being ferried to the site by tractor, quad bikes and military vehicles.

Spanish train operator RENFE put on a special train to take emergency workers to the site.

The civil guard, fire brigade and regional civil protection all sent units to the scene and many of the injured were treated on-site before being taken to hospitals in the region.

One seriously injured person was taken by helicopter to the Virgin de Rocio Hospital in Seville.