The CBI has registered three FIRs on the instructions of the Centre which had forwarded these cases to the agency, officials said.
The three FIRs pertain to the alleged fake encounter, the violent protests that followed and the death of a person, believed to be witness to the encounter, in the police firing.
Several groups in Rajasthan had demanded a CBI probe claiming it was a staged encounter.
Singh, wanted in several cases including of murders, was killed on June 24 last year (when he was 47 years old) in a police encounter at Malasar in Churu district.
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