Some plates which were removed from the track have been shown to the local police

Nitish Kumar, railway minister

The train was on its way from New Delhi to Patna in eastern Bihar state when it crashed near the city of Jaunpur.

Investigators said there was evidence the track had been tampered with.

"Some plates which were removed from the track have been shown to the local police," Railways Minister Nitish Kumar said.

Northern Railways spokesman Devender Singh said: "Preliminary investigations point to the possibility of sabotage," adding that mechanical failure had been ruled out as a cause of the crash.

Rescue effort

The Shramjeevi Express was carrying 1,800 passengers when it derailed on a bridge.

Most of the passengers were asleep at the time of the accident.

Rescue workers pulled trapped survivors from the wreckage, while at least three victims had to undergo amputations, officials said.

Medical teams rushed to the scene from the state capital of Lucknow, some 200 kilometres (125 miles) from the crash site.

Work to clear the line was continuing on Monday, as two cranes lifted the derailed carriages off the track.

The Indian Railways, which daily runs 11,000 trains on the world's second largest network, has nearly 300 accidents a year.

Two-thirds of those accidents are blamed on staff negligence.