The Criminal Investigation Department (CID) has been asked by the state government to conduct an inquiry into the incident at Nandigram that left chief minister Mamata Banerjee injured on March 10.

The Election Commission of India had asked the state chief secretary and DGP to initiate action against security personnel who failed to prevent the incident.

“An order to hand over the inquiry to the CID was issued on Saturday. The CID has been asked to file the investigation report at the earliest,” said a senior bureaucrat.

Senior officers in the CID said the probe would focus on three key issues — how the chief minister injured her left leg while in a car, what was the series of events that resulted in her cringing in pain with her injured left leg despite a security ring around her and whether there was any criminal plot to the incident or it was just an accident.

“A Special Investigation Team (SIT) has been set up and the members would be visiting the area on Sunday to talk to some of those who were present when the incident took place including a few shop owners of the local market,” said a senior CID officer.

Sources said the decision to hand over the probe to the CID was taken after the progress of the police inquiry into the incident was slow and the chief secretary and the DGP had to seek more time from the EC to follow its instruction of initiating action against the guilty. The chief secretary and the DGP had been asked by the EC to initiate action against proximate security personnel by March 17 but the deadline could not be met. The poll panel has already removed director security, Vivek Sahay and East Midnapore SP Pravin Prakash.