During the examination Vahanvati was asked about his legal opinion given to the Telecom Ministry when the spectrum process begun, agency sources said.
However, Vahanvati told reporters that CBI approached him only for some clarifications and he was not questioned.
He said that DoT had earlier sent him a press release and had sought his opinion on it. He had sent back the release to the DoT after making some notings on it, the AG said.
But the notings on the release had been tinkered with and the CBI wanted to know about it from me, he said.
Vahanvati's statement to CBI was taken on the legal opinion relating to a press release issued by the Department of Telecommunications (DoT) on the allocation of 2G spectrum on a first come-first-serve basis.
In the statement, the Attorney General is understood to have told the CBI that two paragraphs of the press release had been deleted to suit the needs of some people following which the CBI carried out forensic examination of the handwriting in the original press release by experts.
The sources said the experts had claimed to have found that the document was forged and some words had been included separately.
Janata Party leader Subramanian Swamy had written to Prime Minister Manmohan Singh urging him to withdraw Vahanvati from spectrum hearings as he had become a party to the decision taken by Raja by giving his opinion.
The statement of the Attorney General is seen as crucial by the agency as it would help it in strengthening the case against Raja who was mainly relying on the fact that he had taken a policy decision and that it could not help in establishing alleged forgery and malafide intentions of former Telecom Minister and others involved in the case.
The CBI also quizzed Subbarao, who was the then Finance Secretary, and recorded his statement. He had raised questions over the entry fee for mobile operators ahead of the spectrum allocations.
Subbarao is understood to have told the CBI that he had suggested staying the implementation of the decision on spectrum and also sought previous communications granting permission and the dates on which the decision was taken.
The letter was sent by the then Finance Secretary by end of November 2007 and the DoT is alleged to have ignored it and headed for allocation of 2G licenses in January 2008.
The Government, in an affidavit filed in the Supreme Court on the 2G spectrum issue, had also stated the then Finance Secretary had raised certain queries on November 27, 2007, regarding the entry fee.
A reply to this was given by the Telecom Secretary on November 29, 2007. However, there was no further communication on the issue.
Subbarao had earlier this month appeared before the Public Accounts Committee of the Parliament after which PAC Chairman Murli Manohar Joshi had said Subbarao shared "accurate information" with the members on the controversial issue.
A communication sent to RBI seeking Subbarao's reaction has not been answered yet.