Special counsel Robert Mueller on Thursday asked for more time to sift through the “voluminous and complex “evidence collected from Roger Stone’s devices.

Prosecutors say they have “several years” worth of evidence including FBI case reports, search warrant applications, bank and financial records and the contents of “numerous” cellphones and computers.

In a court filing, they asked Judge Amy Berman Jackson to designate the case as “complex,” which would lengthen the time for trial preparation.

Under federal law, a trial must start within 70 days of arraignment, unless a judge gives it a “complex” designation and stops the clock.

Mr. Mueller also asked for a protective order ensure the confidentiality of evidence collected against Mr. Stone as prosecutors began sharing it with defense attorneys.

Authorities arrested Mr. Stone last week and he was indicted on seven criminal charges, including obstruction of justice, making false statements and witness tampering. He pleaded not guilty before a federal judge in Washington on Tuesday.

Mr. Stone next heads to court Friday for a status conference hearing before Judge Jackson.