Union home minister P Chidambaram today said Maoists or its front groups could be behind the attack on Jnaneswari Express, a theory contrary to railway minister Mamata Banerjee's claim that it was a conspiracy of the West Bengal government.

Chidambaram said the Railways favoured a CBI probe into the incident which claimed 148 lives but the state government's view on it has not been received yet.

"The needle of suspicion points to Maoists or frontal organisations of CPI Maoists," Chidambaram said during his monthly media briefing.

"However, the identity of the culprit can be established only in the investigations. Railway ministry has suggested that there should be a CBI inquiry. We have asked for West Bengal government's views. We have not yet received their views," he said.

Asked about reports of blast on the track, Chidambaram said, "I have been told by the West Bengal government and other police officials who visited the site that so far there is no trace of any explosives. The West Bengal government is on record saying panrole clips were removed and track was cut.

That is also prima facie established. Only further investigations will bring out the truth."

Mamata Banerjee and her bitter rivals, the CPI-M got into a no-holds barred fight on who was to blame for the attack. Trinamool sees a conspiracy hatched by the state government while the CPI-M accuses Banerjee of being ineffective.

On May 28, 13 coaches of the Maharashtra-bound express were derailed and was later hit by a goods train coming from the opposite direction.