The Central Bureau of Investigation (CBI) formed a special investigation team (SIT) led by a deputy inspector general (DIG) rank officer to investigate a larger conspiracy and inter-state ramifications in the murder of Chandranath Rath, aide to West Bengal chief minister Suvendu Adhikari, people familiar with the development said on Tuesday.

The federal agency already registered a case after taking over the first information report (FIR) from West Bengal police.
Officials said that the SIT, led by DIG Pankaj Kumar Singh is currently in the process of taking over from local police and examining all cases documents so far, besides taking the custody of three men— Mayank Raj Mishra and Vicky Maurya (both from Bihar) and Raj Singh (from Uttar Pradesh).
Singh is allegedly involved in at least 15 murder cases in Bihar and Uttar Pradesh and is suspected to be the main contract killer in the Rath murder case, an officer said.
CBI officials said that the seven-member SIT formed under Pankaj Kumar Singh, an IPS officer, comprises some of the best investigators drawn from various units of the agency. The team members will report to the joint director in Kolkata.
The SIT, officers added, reached the crime spot along with the forensic experts to re-create the scene.
Rath, 41, a former Indian Air Force serviceman, was shot dead from close range inside his SUV while returning home in the Madhyamgram area of North 24 Parganas district on the night of May 6, two days after BJP swept to power in the state, ousting the Mamata Banerjee-led TMC government after 15 years. His driver, Buddhadeb Bera, who was also shot, is admitted to a private hospital in Kolkata; a third person, Mintu, was unhurt. “Probe is on to trace those who hired these killers. The motive will be apparent once we nab them,” an investigating officer said, requesting anonymity.
On the night of the murder, the assailants chased Rath’s vehicle for around seven kilometres before forcibly stopping his car. Rath was shot five times and died on the spot. Bera was shot thrice. Soon after the crime, Adhikari alleged that Rath was killed because of their close ties. BJP leaders across the country blamed the TMC for the murder. The TMC, in turn, demanded a CBI probe.