Fire officers and police are investigating after a fire at a comprehensive school in Conwy.
A portable cabin at Ysgol Emrys ap Iwan in Abergele was badly damaged in the blaze at 1825 GMT on Thursday, and a second cabin was affected by the heat.
It is the latest in a series of arson attacks at schools across north Wales.
Last month two classrooms and the nursery at St Mary's primary, Flint, were damaged when piles of books were set on fire.
Two attacks at nearby Ysgol Gwynedd damaged a mobile classroom and left part of a building smoke logged.
Forensic experts are conducting tests to determine whether the attacks on the two schools are linked.
Also last month fire crews were called twice to a Wrexham school, Ysgol Y Gaer, Gwersyllt, to deal with blazes in the bin compound of the school.