A COMPUTER "cooking" overnight sparked a blaze which left classrooms at a Worcester high school badly damaged by smoke.

Nunnery Wood High headteacher Alan Brodrick said it was "too early" to put a figure on the cost of repairing the Spetchley Road school.

A member of staff spotted smoke billowing through the English centre this morning when she arrived for work.

The fire alarm in the building had failed to go off.

"A processor in a computer had burnt out and set fire to both the machine and the one next to it," said Mr Brodrick.

"This caused extensive damage to the classroom, the corridor and several others."

An insurance loss adviser would be contacted as soon as possible, he said.

"The fire brigade believed the computer may have been 'cooking' overnight," said Mr Brodrick.

"I was alerted by a teacher from the English department, Claire Rowe, at 7.35am and then I called the fire brigade. It's worrying the fire alarm didn't sound."

Mr Brodrick said it was the first time in 27 years as a teacher he had had to cope with such a situation.

Three crews, two from Worcester and one from Droitwich, were sent to deal with the fire at in the two-storey centre.

"The classrooms that have been affected would normally be used by Year 9," said Mr Brodrick.

"But because pupils in Year 11 have examinations, fewer people are in the school at the moment than normal, so we'll be able to distribute the year nines to other classrooms."

Students had used the computer network to save essays, but the headteacher said their work was safe because the data had been fed to a hard-drive away from the computer that had suffered meltdown.

"The firefighters used ventilation fans to disperse the smoke," said fire brigade spokesman Alec Mackie.

"The cause of the fire is still being investigated, but it's believed to be an electrical fault."