ASBSESTOS found at a Colchester school was first spotted by inspectors looking at how ceiling debris crashed into a class full of pupils, it has emerged.

ASBSESTOS found at a Colchester school was first spotted by inspectors looking at how ceiling debris crashed into a class full of pupils, it has emerged.

The Health and Safety Executive (HSE) revealed yesterdayits inspectors discovered the potentially harmful substance at Alderman Blaxill School while they were investigating an official complaint from teaching unions.

The 550-pupil school has been closed all week and will remain so until early next week to allow asbestos safety work to be carried out.

It was not thought the asbestos presented any health risk to children at the Paxman Avenue school.

A HSE spokeswoman said teachers at the school had complained to their unions after debris fell into a classroom while work was being carried out on a skylight last September.

Two months ago, teaching unions approached the HSE about the incident and during the investigation inspectors discovered asbestos in three areas, which they said needed "encapsulating" - a form of protective painting.

Although the school was criticised over the September incident, the HSE decided not to prosecute because so much time had elapsed, the spokeswoman said yesterday.

She added: "The HSE advised that the school should have carried out a full survey before that work started.

"The work should have taken place while the classroom was unoccupied and the contractors should have had dedicated access to the work area.

"The HSE then recommended a full survey should be carried out which began around two months ago.

"This revealed three areas with asbestos, which needed encapsulating."

Ian Poulter, the school's headteacher, said "lessons had been learned" from the September incident and he admitted the HSE's asbestos findings had been "helpful" in highlighting the existence of the substance during a routine survey at half-term, which led to the school's closure.

Around 550 pupils have been off all week while emergency repairs are carried out. It had been hoped they could return on Monday.

In a statement Mr Poulter expressed "considerable regret" that would not be the case.

He added: "Unfortunately not all the paperwork has been cleared and workers will still be on site over the weekend.

"We hope early next week, pupils will be allowed to come back on a phased basis."

Jerry Glazier, Essex NUT general secretary, did not want to discuss the complaint to the HSE and added: "What's important is that the school did exactly the right thing in closing down after the half term survey."