The National Investigation Agency (NIA) has allegedly picked up two people for interrogation in connection with the blast that occurred on the railway tracks in Buxar district last week.

The blast on the railway tracks had occurred between Buxar and Baruna railway stations on Monday soon after the Varanasi-Sealdah (Upper India) Express crossed it. The train was stopped at the explosion site for a few minutes.

Sources said that an NIA team visited Bolhara village under the jurisdiction of Dharahara police station in Bhojpur district on Sunday and took two persons into custody. The team left for an undisclosed location with the detainees.

Police officials from both Bhojpur and Buxar districts feigned ignorance about any raid by the NIA.

"I am not aware of such action," said Buxar superintendent of police Opendra Kumar Sharma. His counterpart in Bhojpur - Kshatranil Singh - also denied having any knowledge.

Residents, however, confirmed the police team's visit to the village.

"The local police were not taken into confidence before the NIA's raid," said a resident.

Patna superintendent of rail police Jitendra Mishra said they are still waiting for the forensic report.

"We will share the results of the forensic science laboratory (FSL) report if it comes to my office," Mishra told The Telegraph on Sunday.

Superintendent of rail police Mishra said nobody has been arrested in the case yet, and he attributed the delay in police action to the forensic sciences report. He added that no splinters were found at the site of the blast

An FSL team had visited the spot and gathered samples from there. "Prima facie it seems that fire crackers were burst on the track," Mishra said. The NIA is already probing the planting of a bomb on the railway track near Ghorasahan in East Champaran district on October 1, 2016, and has apprehended the involvement of Pakistan's ISI in the case.