The CBI has registered a case against unknown persons in the alleged murder of IPS officer Narendra Kumar Singh who was mowed down by a tractor trolley purportedly owned by sand mafia in Morena district of Madhya Pradesh on March eight.

The case was registered by the CBI after Centre issued a notification for the probe by central agency on the request of Madhya Pradesh Chief Minister Shivraj Singh Chouhan.

The special crime unit of the agency has registered a case of murder against unknown persons.

The MP CM had ordered a judicial inquiry into the matter and also recommended a CBI probe at the instance of the slain officer's wife, Madhurani Tewatia, an IAS officer.

30-year old Singh, a 2009-batch officer, was posted at Banmore in Morena district as Sub Divisional Officer of Police (SDOP) a month ago and had taken on the mining mafia by seizing number of trucks and tractors engaged in illegal quarrying.

The incident occurred on Holi when Kumar, who was out on patrolling in his official jeep, saw the trolley loaded with stones. He signalled the driver to stop but he did not pay heed. So, he followed the vehicle, cut in and stood in front of the vehicle after getting down from his jeep.

But the tractor driver drove on and knocked him down, crushing him to death. The driver was arrested.