"We suspect Javed may have been involved in some way in the conspiracy behind the Sadiq Jamal fake encounter, as he was an informer of an IB officer. We are verifying our suspicion; the probe is at a crucial stage," said the source.
A home ministry source, however, rejected the CBI's suspicions saying, "Javed Shaikh was not an IB informer."
The CBI is probing two possible motives behind the killing of the four. Either the deceased may have witnessed a crime and were thus potential threats or the accused police officers may have craved for career-related benefits, according to the source.
The CBI is to submit its supplementary charge sheet in the June 2004 fake encounter case on the conspiracy behind it, said the source.
Last December, the CBI had filed its charge sheet in the Mehtar encounter case against eight Gujarat policemen invoking charges of criminal conspiracy and murder.
According to the probe findings, a retired assistant director of the IB had allegedly generated a fake source report on Mehtar. He was later allegedly bumped off in a fake encounter on January 13, 2003, in Ahmedabad.