Two passengers trains in India were derailed in separate incidents Sunday, leaving at least 67 people dead and about 200 others injured.

All of the fatalities occurred in a derailment in the northern state of Uttar Pradesh. Rescuers were searching Monday for more survivors

in the wreckage of the Kalka Mail train that jumped the track en route to New Delhi. More than 100 were injured.

The cause of the crash was not immediately clear.

Hours later on Sunday, a second train derailed in the northeastern state of Assam, injuring 100 people. No fatalities have been reported.

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

On 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.