Supreme Court officials are escalating their search for the source of the leaked draft opinion that would overturn Roe v. Wade, taking steps to require law clerks to provide cell phone records and sign affidavits, three sources with knowledge of the efforts have told CNN.

Some clerks are apparently so alarmed over the moves, particularly the sudden requests for private cell data, that they have begun exploring whether to hire outside counsel.

The court's moves are unprecedented and the most striking development to date in the investigation into who might have provided Politico with the draft opinion it published on May 2. The probe has intensified the already high tensions at the Supreme Court, where the conservative majority is poised to roll back a half-century of abortion rights and privacy protections.

Chief Justice John Roberts met with law clerks as a group after the breach, CNN has learned, but it is not known whether any systematic individual interviews have occurred.

Lawyers outside the court who have become aware of the new inquiries related to cell phone details warn of potential intrusiveness on clerks' personal activities, irrespective of any disclosure to the news media, and say they may feel the need to obtain independent counsel.