Some 12 carriages of the Rajdhani Express, which was travelling from the capital New Delhi to the northeastern state of Assam, toppled over at around 2:00 am (2030 GMT) in Bihar state's Saran district.
"Prima facie, it appears to be a case of sabotage," Railway Board chairman Arunendra Kumar told the Press Trust of India (PTI) news agency. "There was a blast on the track, which could have caused the derailment."
Maoist rebels had earlier called for a strike in the area to protest against the security forces.
Railway Minister Sadananda Gowda said there was no confirmation about what caused the derailment.
"As far as the Rajdhani Express is concerned we practically don't have much news about the cause of derailment (but) of course there was a bandh (shutdown) call given by Maoists," he told reporters.
A senior police officer, Superintendent Sudhir Kumar, said that a thorough investigation had been ordered into the incident, adding that a "technical fault" could also have been the cause.
If confirmed as an attack by the Maoists, it would be the first by the insurgents since Prime Minister Narendra Modi's right-wing Bharatiya Janata Party came to power last month after an election victory over the ruling Congress.
Separatist insurgencies affect large swathes of India's northeast, northwest and central regions, including the states of Chhattisgarh, Orissa, Bihar, Jharkhand and Maharashtra.
Many of the rebels say they are fighting authorities for land, jobs and other rights for poor tribal groups.
The Maoist insurgency has cost thousands of lives.