The head of the Senate Homeland Security Committee is asking the Justice Department to disclose whether encryption was used in the Dec. 2 terrorist attack in San Bernardino, Calif.

“Please provide any evidence of encrypted communication retrieved from the electronic devices of [Syed] Farook and [Tashfeen] Malik that may have masked specific plans and logistics,” requests the letter from Sen. Ron Johnson, R-Wis., addressed to Attorney General Loretta Lynch on Monday.