According to the fire service’s website, crews from 18 stations had attended the scene since it was first reported.
“We still have six fire appliances at the scene plus special appliances and firefighters continue to use the aerial ladder platforms, water jets and a high-volume pump to bring water to the scene,” a fire service spokesperson added.
A Facebook post from Devon and Cornwall Police, external at 00:40 said road restrictions remained in place between Exeter Road at the junction with Fatherford Lane and the B3260 at Belstone overbridge.
According to the Dartmoor Multi-academy Trust, the Promise School opened officially in September 2022, with students moved into the “custom-built site in the centre of Okehampton” from the start of the 2023/24 academic year.
The trust said the school provided specialist support for about 100 children aged four to 16.