Maoist guerillas are believed to be behind the blast in their West Bengal stronghold. If confirmed it would mark a major escalation of their insurgency in the state and a shift from military to civilian targets.
Indian prime minister Manmohan Singh has described the Maoist rebellion as the country's greatest internal security challenge - they are a powerful force in one-third of India's 600-plus districts.
The explosion follows a number of Maoist attack attacks in recent weeks, including an ambush which killed 76 Indian paramilitary police in Chhattisgarh and an attack on a bus which left 35 dead. This time the attackers struck at 1:30am as the Mumbai-Calcutta Gyaneshwari Express passed through Jhargram in West Midnapore, West Bengal, just over 80 miles from its destination.
The driver heard an explosion which derailed 13 of the train's coaches and hurled five of them into the path of an on-coming freight train. Ten of those derailed were sleeper coaches.
India's railways minister Mamata Bannerjee said the incident was "definitely sabotage" and that a bomb attack had derailed the train. "From whatever I have been told the apprehension is the Maoists were involved," she said.
Police investigating the attack said they were also exploring whether the removal of the track's "fish plates" by saboteurs had caused the derailment and collision.
"The driver heard a loud noise which indicates there could be a blast. A detail investigation will reveal more, but definitely there was lot of tinkering done to the tracks," Vivek Sahay, a senior railway official, said.
Television pictures showed the mangled carriages as rescue workers fought to cut survivors from the wreckage.
One reporter described a scene of chaos and panic.
"People are crying. Rescuers are struggling to save the survivors and get the bodies out," Naresh Jana said.
"I can see body parts hanging out of the compartments and under the wheels.
I can hear people, women, crying for help from inside the affected coaches."
The Maoists insurgents are known in India as "Naxalites" – they began their campaign in Naxalbari, in northern West Bengal in support of peasants demanding land reform in 1967. They have since grown in strength in India's poorest and most rural states. They now are a powerful force in Chhattisgarh, Orissa, West Bengal, Bihar, Madhya Pradesh and Jharkhand.
Their popularity has grown in the last few years among peasants and tribesman as government-backed mining companies have moved into their districts and seized their land.
They have threatened to launch a new terror campaign in Orissa to halt plans by Britain's wealthiest man, Lakshmi Mittal to open steel plants in state
Their recent attacks have been in response to an operation by government forces to flush them out from their jungle strongholds.
At least 65 people were killed and over 200 injured when a train derailed in West Bengal, India. Suspected  rebels triggered the attack which occurred in the Howrah-Kurla Lokmanya Tilak Gyaneshwari Super Deluxe Express. The train, which runs from Kolkata to Mumbai, had thirteen coaches derailed, five of which were subsequently struck by a freight train coming in the opposite direction.

The train derailed near the city of Sardiha, about 90  (150 ) southwest of the state capital of Kolkata. The region is a Maoist stronghold where multiple attacks have occurred in the recent past. The exact cause of the disaster was unclear, with some officials claiming an explosion had led to the attack, while some unaffected passengers stating they heard no blast. 

Police officials, including Bhupinder Singh, the head of police of the state, said the metallic parts which held parts of the rail track together were missing and labeled this as an act of sabotage. Singh blamed the Maoists for the attack stating policemen had found Maoist leaflets at the scene.

However, the driver said he had heard an explosion in the attack which derailed as many as ten passenger coaches. The country's railways minister  said the combined effect of sabotage to the tracks and a bomb blast led to the incident. According to her, there was "definitely sabotage" and the bomb blast had led to the derailment. "From whatever I have been told the apprehension is the Maoists were involved," she added. Police officials mentioned they were investigating whether the removal of the "fish plates" was the primary cause of the attack.

"The driver heard a loud noise which indicates there could be a blast. A detail investigation will reveal more, but definitely there was lot of tinkering done to the tracks," a senior railway official, Vivek Sahay, said.

The incident occurred at around 1:30 a.m. local time, and police forces and local medics took an hour to rech the site. Lack of roads and the fear of an ambush by Maoists slowed rescue operations. Passengers complained of the slow operations; some of them claimed luggage and valuables were stolen in the confusion.

E. Mitra, a doctor at the nearby Kharagpur Railway Hospital, noted 30 bodies had been taken to the hospital. But "a lot of dead bodies are strewn under the derailed carriages," he added. Home Secretary of the state, Samar Ghosh, said 65 bodies had been found till then.

 helicopters came to the scene at dawn as local television footage showed onlookers standing on the top of the affected carriages, as soldiers cut holes in the roofs with a gas-powered circular saw.

"People are crying. Rescuers are struggling to save the survivors and get the bodies out," Naresh Jana, a witness, said. "I can see body parts hanging out of the compartments and under the wheels. I can hear people, women, crying for help from inside the affected coaches."

"There was a massive jerk, and we thought the Maoists had stopped the train to hijack it," another unidentified witness told local media. "But thank God it was an accident ... at least many people are saved. This area is very dangerous, very dangerous."

The railways minister of India announced a compensation of $11,000 and a job in her ministry for the families of the dead and $2,200 for those wounded.

The Maoists guerillas who are known as "Naxalites" in India are powerful force in Chhattisgarh, Orissa, West Bengal, Bihar, Madhya Pradesh and Jharkhand, which are the relatively poorer states of India. In the past few years, poor or landless peasants and tribesman have rendered their support towards the insurgents, due to the wealth gap and as a result of the former losing their land to government-aided mining companies.