A 10-member Special Crime Investigative unit of the CBI reached Kunda tehsil in Pratapgarh district on Friday to probe Saturday's killing of a village pradhan, his brother and DSP Zia-ul-Haq.
The CBI took over the case on recommendation of the Uttar Pradesh government after the demand was made by the slain DSP's wife Parveen.
The CBI on Thursday filed file four FIRs in the case, in which 23 persons, including Kunda MLA Raghuraj Pratap Singh alias Raja Bhaiya, have been named as accused.
Mr.Singh and four others, Gulshan Yadav, Hari Om Srivastava, Rohit Singh and Sanjay Singh have been booked under various sections of the IPC, including murder (302), criminal conspiracy (120b), rioting and intentional insult to provoke violence (504).
Out of the four FIRs, two pertain to the killing of the DSP and rioting in the village.
The other two cases concern the murder of the village pradhan Nanhe Yadav and his brother Suresh, in which four persons have been named accused.
The team, led by DIG Anurag Garg and accompanied by forensic experts, visited the crime scene in Ballipur village and the Hathgawan police station, sources said.
However, the officers were tight lipped on the investigation.
Inspector General of Police Allahabad Range, Alok Sharma said he had handed over all the evidences, general diaries and investigation reports to the CBI team.
Superintendent of Police Pratapgarh, L.R Kumar confirmed that the CBI probed both police officials and eyewitnesses to reconstuct the sequence of events.
The CBI also seeked details of call records of the accused to get their location at the time of the incident.
There were speculations that the CBI team could call for a second post-mortem of DSP Haque but there were no reports of it till Friday evening. The deceased officer's uncle Phul Mohammed said since their demand of CBI probe was accepted the family would not press for a second post-mortem.
Ms Parveen had dismissed the first post-mortem report contending that her husband was shot thrice and not once as claimed in the report.
She later retracked from her comments but demanded a copy of the film shot during thr post-mortem examination.
The state police have already booked Raghuraj Singh on charges of criminal conspiracy after Ms Parveen alleged that her husband was killed at the behest of the MLA. Mr. Singh resigned as UP Food and Supply minister after he was made an accused in the case.
The CBI will look to seek custody of the two accused arrested by the state police so far, Rajeev Singh and Sanjay Singh alias Guddu Singh. Guddu Singh, a close aide of the MLA, has also been booked in the murder of the pradhan's brother.
The DSP's missing mobile and service revolver, and the bullet that killed him are yet to be retrieved. It is also not clear whether the pradhan's brother died first or the DSP. The police has clarified that Suresh Yadav was shot buy a 12 bore weapon, and the shots were not fired by their personnel.
The CBI is already probing two cases against Mr. Raghuraj Singh, referred to it by the state government.