Calcutta, July 19: Sniffer dogs today scoured the train crash site for explosives that may have been used to damage the tracks even as rail minister Mamata Banerjee said she was suspicious about the cause of the accident.

For over an hour, four specially trained dogs examined a 1,000-metre stretch of the rail tracks at Sainthia, 190km from Calcutta, where the speeding Uttar Banga Express rammed into the rear of the Vananchal Express.

“Engaging sniffer dogs is part of our routine drill after any major mishap. But we have not got any lead to make us believe there was any sabotage (to cause) a derailment or an explosion,” Dilip Mitra, the additional DGP, rail, said.

Experts from the railways’ safety wing also inspected the tracks for telltale signs of sabotage, that may have caused a derailment or explosion, but found nothing. The railway police have started a probe.

Another railway police officer added: “We also took the dogs to the area beside the tracks, but it did not work as the dogs failed provide any suspicious lead.”

However, before leaving for the site, Mamata hinted at possible sabotage. “We have some doubt in our mind. Whatever happened is not a casual thing. We will take all strong steps against those who are behind this,” she said in Calcutta.

An Intelligence Branch (IB) officer said all possibilities were being explored. “The railways are conducting a probe into any fault of their department and we are focused on whether there was involvement of any outsiders.”

The IB was also trying to probe if Maoists had any hand in the crash like in the Jnaneswari Express mishap, although Birbhum district is not a hotbed of the rebels.