Further, West Bengal Director General of Police (DGP) Bhupinder Singh asserted the Maoists and some cadres of the Maoist-backed People’s Committee against Police Atrocities (PCPA) were behind the incident. "We have identified a number of persons all of whom are Maoist squad members and supporters of the Maoist-backed Police Santrash Birodhi Janasadharaner Committee (also known as the PCPA). Raids are being conducted to nab them. We are also suspecting the role of a railway linesman but are still verifying whether he had connived with the Maoists or was forced into the job." [Earlier Police claimed that posters from the PCPA had been found at the scene, claiming responsibility for the attack. The posters said that the rebels had demanded withdrawal of joint SFs from Lalgarh and adjacent areas and an end to CPI-M ‘atrocities’.] Significantly, the DGP claimed that investigations by the Crime Investigation Department’s (CID) forensic team did not find any sign of explosives or an explosion on the track. The CID has claimed to have "definite evidence" that Maoists were involved in derailing the Express, based on intercepts of conversations on several rebel leaders' mobile phones.
Meanwhile, a high-level intelligence report submitted to Chief Minister late in the night of May 28, blamed the Manikpara Lodhasuli militia unit of PCPA, led by 40-year-old Umakanta Mahato and Bapi Mahato (aged 20), for the sabotage. Lodhasuli is on the Bengal-Orissa-Jharkhand tri-junction. Police said the Umakanta-Bapi gang could have forced railway gang men and linesmen to help saw the track and remove 120 feet of Pandrol Rail Clips. Over the last fortnight, the SFs had stepped up pressure in the area, and there had been several encounters. Even on the day of the accident, railway employees at Sardiya Station claim they heard gunfire at a location about eight kilometres from the incident site. Six persons had been picked up from nearby villages after the shootout.
The PCPA, however, denied that it was behind the incident. PCPA spokesman Asit Mahato, stated, "We were in no way involved. This is not our act. What can we do if somebody claims responsibility on our behalf?"
The Maoists, meanwhile, have gone into damage-control mode, trying to distance themselves from what is being projected as a ‘rogue unit’ of the PCPA militia. Maoist State committee member Akash issued a press statement saying that they "never target the common people", and further, "The Government can resume train services on the section at night. No harm will be done from our side." Significantly, on May 29, the Railways decided to suspend movement of passenger trains for seven hours at night-time in Maoist stronghold areas during the "black week" declared by the extremists. A Railway's statement said that passenger trains would not run from 10pm to 5am on the Kharagpur-Tatanagar and Kharagpur-Adra sections of South Eastern Railways. The suspension of trains would remain in force till 5am on June 3.
Attacks by the Maoists on the Rail network are not new. On March 22, 2010, the Maoists had blown up railway tracks and derailed the Bhubaneswar-New Delhi Rajdhani Express in Bihar’s Gaya District, leaving pamphlets at the blast site claiming responsibility and threatening more such attacks. The Railways then asked train drivers to slow down in Maoist-affected areas. According to the advisory, Rajdhanis have to move at 75 kilometres per hour instead of their normal speed of 110 kilometres to 130 kilometres per hour. According to Railway Ministry figures, there were 58 Maoist attacks targeting trains and railways property in 2009. The South Eastern Railways alone registered 30 incidents under its jurisdiction. East Central Railways, with its headquarters in Hajipur (Bihar), experienced 18 attacks; while the East Coast Railway registered eight such incidents in 2009, mostly in the Koraput-Rayagada belt where the Red ultras have a strong presence. Maoists have also taken over trains in a show of strength, holding them for hours, on several occasions over the past years. According to partial data compiled by the South Asia Terrorism Portal, there have already been 26 attacks on the Railways in 2010, though none of these had resulted in a fatality this year, before the Sardiya incident.
On April 23, 2010, Mamata Banerjee informed the Rajya Sabha