SAN JUAN, Puerto Rico (AP) — Guards at the Guantanamo Bay prison used “non-lethal force” to quell a disturbance in a recreation yard, a military spokesman said Wednesday, declining to confirm a lawyer’s account that a shot was fired and that one prisoner was injured.

The incident occurred Jan. 2, but only came to light this week after the attorney, Clive Stafford Smith, released a letter he sent to the commander of the prison on the U.S. base in Cuba requesting an investigation.