STAFF are returning to work at the Oxford mail sorting office in Cowley following an explosion.

About 110 staff were evacuated. The incident happened at about 11.30am in an engineering store room, but staff were then told to leave the premises at about 2.30pm as the investigation continued.

The workers were then allowed back into the building just after 3pm after being given the all clear by police.

Royal Mail spokesman Richard Hall said the explosion was not related to an item of mail and no-one was injured with damage limited to a wall in the affected room.

He added: "The incident was some distance away from the mail sorting operation and no mail was damaged. Police are investigating but we understand the evacuation is just a precautionary measure."

Mr Hall said about two hours of work had been lost, which could cause delays to mail deliveries tomorrow.

He added: "We are evaluating the situation and have the option of moving some mail to other centres but disruption is a risk."

Police were called to the depot in Alec Issigonis Way, shortly after noon, by Oxfordshire Fire Service.

Nobody was injured in the incident, although witnesses were treated for shock.

Victoria Bartlett, a spokesman for Thames Valley Police, said it was not clear whether the explosion was the result of an industrial incident or for another reason.

She added that the local authority's environmental health department have been informed and as soon as it is safe to do so an investigation will begin to determine exactly what has happened.