The agency, which had filed its charge sheet in the alleged fake encounter has accused Shah of criminal conspiracy, murder and destruction of evidence, besides other charges.
During the probe, CBI claimed to have come across proofs which shows that at least 16 calls were allegedly exchanged between the then Home Minister, DIG DG Vanzara and SP Rajkumar Pandian between December 20 and 31, 2006.
Tulsiram Prajapati, an eye witness in the encounter of Sohrabuddin Sheikh, was killed in a fake encounter allegedly by Gujarat Police in Banaskantha district on December 28, 2006.
Sources said the agency has already questioned Shah with regard to his telephone conversations with the two IPS officers within 10 days of encounter.
Call details of Shah accessed by CBI showed that he allegedly spoke to Pandian a day before the encounter took place, they said.
The minister had claimed innocence in the matter and told CBI that the calls were made with regards to different cases handled by the police officials, they said.
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He had told CBI that his conversations with the officers were related to another absconding gangster whose calls were monitored by Pandian as ATS SP.
Shah had denied that he had any knowledge about Tulsiram encounter prior to the incident.
CBI has filed the charge sheet in the encounter but it was not taken on record by the court due to question of jurisdiction. The court will decide in the matter after conducting hearing next Monday.