Police in Pakistan say they are holding 22 suspects over attacks on schools in the Diamer District.
More than a dozen schools were subjected to arson on the night of 2 August. Police say in some cases books were found to have been thrown out of the buildings and also set alight.
No casualties were reported.
In an update on the investigations, officials claim 87 suspects were taken into custody, with 22 of those found responsible for the attacks.