In India, two passengers trains were derailed in separate incidents Sunday, leaving at least 31 people dead and about 200 others injured.

Rescuers in the northern state of Uttar Pradesh, the site of the first derailment, were searching for survivors in the wreckage of the Kalka Mail train that jumped the track en route to New Delhi Sunday afternoon. At least 31 passengers were killed and 100 injured in the incident.

The cause was not immediately clear.

Hours later, the second train derailed in the northeastern state of Assam, injuring another 100 people.

Local police suspect a remote-controlled bomb caused four coaches of the Guwahati-Puri express train to be thrown off the tracks.

It was the third train accident in India in the last four days. Last Thursday, at least 35 people died at a railway crossing in Uttar Pradesh when a train rammed into a bus returning from a wedding.

India’s railway network is one of the largest in the world, carrying about 14 million passengers each day. Accidents are common, with most blamed on poor maintenance and human error.