Italian police arrested 13 prison guards on suspicion of torture and ill-treatment of juvenile detainees, Milan prosecutors said on Monday.

In addition to the 13 guards, 12 of whom work at the Cesare Beccaria juvenile detention centre in Milan, eight other officers have been suspended, prosecutors said in a statement.

The juvenile prison is staffed by 50 guards, but has not had a director for 20 years. The prison made no immediate comment on the arrests, while the main guards’ union issued a statement saying it was “dismayed” by news of the investigation.