No incisive leads indicating the origin or the grade of explosives used in the blast at the Nimtita railway station were uncovered till Friday even though the CID, bomb squad and forensic experts have been scouring the area.

Junior labour minister Jakir Hossain and 26 people accompanying him were injured in the blast at the railway station in Murshidabad district around 10pm on Wednesday. The minister had reached the railway station to board the Calcutta-bound Teesta-Torsa Express when explosives suspected to have been kept on the platform went off.

“We are collecting blood-smeared soil and rock samples hoping for a lead, but as of now, we are still unclear about the sophistication of the explosives or their origins. The remains and splinters will help our probe,” said scientist Chitrankar Shankar of the Forensic Science Laboratory who arrived with his team at Nimtita from Calcutta on Friday.

Separate teams of CID and bomb squad officials from Calcutta had reached the site on Thursday morning and sealed off the area, disrupting train services for a day for their investigations that spanned the surrounding areas.

On Friday, the probe teams recovered splinters, suspected to have been used to make the explosive, 30 metres away from the station. The portion of a human finger was found 100 metres away from the roof of the railway station’s ticket counter.

“The recovery of a part of the human finger 100 metres away from the blast site goes to show the power of the explosion,” a CID sleuth said.

Inspector general of police (south Bengal) N.K. Varma and other senior police officers also inspected the blast site on Friday but refused to comment on the status of the probe.

Divisional railway manager (Malda) Jitendra Kumar also visited the site and issued a press release later on Friday. Sources said the Government Railway Police had filed a fresh report on Friday at Azimganj police station in connection with the incident.

Nimtita station was sanitised and thrown open to the public on Friday evening but the CID and the police continued with the investigations.

Behrampore MP and state Congress chief Adhir Chowdhury demanded that the inquiry be handed over to the CBI.

Chowdhury suggested that “partisan” forces could hamper the outcome if the investigation remained in the hands of the CID, which works under the state government.

“We are demanding an immediate CBI inquiry into the incident,” he said while speaking to reporters after inducting Trinamul turncoat and Murshidabad zilla parishad chairman Musharraf Hossain into the Congress on Friday evening.