Powerful explosives other than RDX were used in the blast in a coach of the Haldibari-Siliguri passenger train that killed seven persons on Monday, West Bengal Home Secretary P R Roy said in Kolkata on Wednesday.
"Powerful explosives and not RDX were used in the explosion as per intelligence reports available," Roy said.
He said metal pellets were collected from the scene of the explosion that occurred at Belakoba in Jalpaiguri district on Monday.
The nature of the blast, Roy told PTI in Kolkata, had striking similarity to a recent explosion at a marketplace at Barovisa in Alipurduar near the West Bengal-Bhutan border.
"RDX was also not used in the Barovisa blast," he remarked.
"The same kind of powerful explosives were found during the blast in a market in Guwahati on November 5," Roy said.
Intelligence sources had earlier said in Siliguri that RDX might have been used to trigger the blast in the train.
Roy, who refused to disclose if any breakthrough had been made in the probe into the blast, said no arrests had been made as yet.
Meanwhile, West Bengal Sports Minister Subhas Chakraborty said the Centre cannot avoid responsibility for Monday's blast.
Speaking to reporters after visiting the injured in hospital, he said it was the Centre's responsibility to guard the borders.
"Central intelligence also failed to provide information. Naturally, the Centre cannot avoid responsibility for the blast," he said.
RDX, which appeared to have been used to trigger the explosion at Belakoba, might have been brought from outside the country by a terrorist group, said Chakraborty, who was despatched by Chief Minister Buddhadeb Bhattacharya to the site of the attack.
Commenting on compensation given by the NF Railways, he said the state government would demand that Rs 5 lakh be paid to the next of kin of those killed.
"We will write to the Railway Board and even the prime minister on this," he said.
NF Railway PRO Taraknath Bhattacharjee said the Rs 15,000 announced for the kin of each of the dead, Rs 5,000 for the seriously injured and Rs 500 for those with minor injuries was an immediate grant and not the total compensation.