Image copyright Reuters Image caption Rescuers are using heavy machinery on the wrecked carriages

At least 17 people have died and another 40 have been injured in a train crash in Pakistan, local media said.

Two trains collided early on Thursday morning near Landhi railway station in the southern city of Karachi.

Initial reports said that one of the trains had been given the wrong signal and at least two carriages had overturned following the crash.

But railway official Nasir Nazeer said the collision's cause could not yet be determined.

All trains out of Karachi have been halted temporarily and rescue workers are at the scene.

TV footage showed serious damage to the trains, and local newspaper Dawn reported that many people were trapped under the wreckage.

Train accidents are common in Pakistan, whose extensive colonial-era railway network has suffered from decades of decline.