A mother has criticised a decision not to evacuate a primary school before bomb disposal experts carried out a controlled explosion at a Second World War munitions store and chemical waste dump.

The mother, who did not want her name published, said: "It was potentially very distressing for the children after what we have all seen on our television screens during and after the terrorist attacks on the World Trade Center in New York."

Bomb disposal experts detonated a number of old photo-flares, which were dug up next to Chilton Primary School, near Didcot. The 18-acre waste dump is currently undergoing a multi-million-pound clean-up, which has led to the discovery of forgotten stocks of ammunition and bombs.

Often these have been detonated during school holidays but sometimes small explosives have been detonated on the site during school terms.

On Wednesday last week some of the flares - which were left behind when the site was abandoned after the war - were destroyed at the end of the day when the children had gone home.

However, Explosives Ordnance Disposal (EOD) experts from RAF Wittering, in Cambridgeshire, then returned on Thursday with more explosives to detonate the remainder of the flares, which were used to illuminate bombing targets at night.

An EOD spokesman said there was no danger to the school or nearby residents, although the Atomic Energy Authority (AEA), which owns the site, warned teachers and householders shortly before the explosion took place at noon.

Colin Hills, chairman of the governors, said: "As has happened on previous occasions, headteacher Christine Dunsdon and her staff were fully consulted and the children were prepared for the controlled explosion.

"None of the pupils showed any signs of being upset by the bang."

But the mother who spoke to the Oxford Mail said some parents were upset that they had not been warned by the school.

AEA Harwell spokesman Nick Hance said: "Unfortunately the EOD were only able to give us an hour's notice of the arrangements and so I personally visited the school and families living in the vicinity. Pupils later took home letters to their families explaining what had happened."

He said the explosion, which rattled windows more than a mile away in the village of Harwell, was louder than expected because of the low cloud and the wind direction.