A joint investigation is to be held between police and firefighters into how a fire which tore through part of a school began.
No arrests have been made by Cleveland Police in relation to the blaze at Rift House Primary School in Masefield Road last night.
The force has said it will be working with Cleveland Fire Brigade as inquiries are carried out into how the fire began.
Today, only year 6 students have been asked to go into school today, with further details to be issued by Hartlepool Borough Council today.
The emergency services were called to the school at 6pm yesterday, with roads around the area closed off to allow firefighters to tackle the blaze.
It is thought the school's nursery has been damaged, with the fire officer working to stop it spreading.
Fire crews from Hartlepool, Middlesbrough and Thornaby stations attended the scene.
Anyone with information is asked to call Cleveland Police on 101.