Launching its probe into Army Chief Gen V K Singh's allegation of having been offered bribe by an equipment lobbyist, the Central Bureau of Investigation on Friday registered a case for alleged irregularities in supply of all-terrain Tatra trucks through state-owned BEML to the Army.

After registering a case against unnamed officials of the defence ministry, Army, BEML and Vectra for alleged criminal conspiracy to cheat and indulge in corrupt practices, CBI officials carried out searches at four places in Delhi, Noida and Bangalore, official sources said.

The FIR also names Vectra group Chairman Ravi Rishi, who is a majority stake holder in Tatra, and the agency is looking into purchases from 1997 onwards, the sources said.

CBI sources said British national Rishi, who is in the national capital for the Defence Expo, was called for questioning in connection with the alleged irregularities in the deal.

As CBI teams began with the searches, the defence ministry came out with a statement saying the defence minister accorded his sanction for a CBI investigation on February  21, 2012, much before the case hit the headlines in the media.

A day after receiving a letter from Ghulam Nabi Azad, on October five, 2009, forwarding the complaints of D Hanumanthappa, addressed to Congress President Sonia Gandhi on BEML, Defence Minister A K Antony had asked the Secretary (Defence Production) to look into the various issues raised in the complaint.