The Justice Department will make a less-redacted copy of special counsel Robert Mueller’s report available to key members of Congress next week, an assistant attorney general said in a letter Thursday evening — though he insisted the information the lawmakers see must remain secret.

The so-called Gang of Eight — the top overall leaders for each party, as well as the top Democrat and Republican on the House and Senate intelligence committees, will be permitted to see the more complete report. So will the top members of the House and Senate Judiciary committees.

Assistant Attorney General Stephen E. Boyd said they’ll have to come over to a special secure room at the Justice Department to look, and they cannot take the materials out. They can take notes, but those notes will have to be tightly controlled as well.

Mr. Boyd said the department would consider “additional access” later.

Access to the broader Mueller report has been a major sticking point.

Though redactions in the version released Thursday were far less than had originally been signaled, Democrats still said there was too much they were prevented from seeing.

The less-redacted report will still preclude viewing of information gleaned from a grand jury.

But the lawmakers with access will be allowed to see information that was redacted from the public report for privacy and security classification.