Official sources said Khan was called yesterday to the agency's office here to remain present and render help in "extricating" data from the hardware of the gadgets seized from his premises during a searches conducted by it on February 9, after a gap of two years.
The agency also wanted to take his voice samples to match them with certain audio evidences, they said.
However, Khan's lawyer Prashant Patil said that taking a voice sample of his client was against the law. "Nothing substantive was asked and Khan was threatened to speak something which the officer shall write on a piece of paper and then the officer would record the voice sample. To this, Khan refused as it's against principles of natural justice," Patil said.
He said Khan told investigators that he was "ready to cooperate with them" but they should record his voice sample in "normal conversation mode". Agency sources said Khan's statement was not recorded and will be done at a later stage, if required. Patil said his 61-year-old client was "medically unwell and in a critical condition".
The agency, which has booked Khan and few of his alleged associates under criminal charges of money laundering in 2011, had swooped down on a dozen premises last month in connection with its probe.
The agency then had said it had seized about Rs 26.30 lakh cash, documents and computer hardware containing information.
The sources said the action (searches on February 9) against Khan and his other associates in the case has come about after a two-year lull as the agency wants to revive the case and bring to light additional evidences so that a trial against him in a Mumbai court could be initiated and the case brought to its logical conclusion.
Khan, who was also jailed under the provisions of the Prevention of Money Laundering Act (PMLA), was released on bail in August last year.