The United Kingdom Atomic Energy Authority and AEA Technology have been fined a total of £8,000 over a chemical incident which raised fears of an explosion in Oxfordshire.

Oxford Crown Court was told on Friday that a standby state of emergency was initiated at Harwell International Business Centre, near Didcot, on September 9 and 10, 1999.

The emergency began when a chemical solution, used to recover silver, was left for 17 days, not the recommended 77 hours.

Members of the Army's Explosive Ordnance Division were called to the business centre, on part of the UKAEA site, and an exclusion zone was set up. Two soldiers were subsequently awarded the George Medal for outstanding bravery.

UKAEA and AEA Technology, a tenant on the site, pleaded not guilty to failing to ensure the safety of employees and non-employees.

Both firms pleaded guilty to failing to make a suitable and sufficient risk assessment.

In mitigation, the court was told scientists and experts investigating the incident could not agree on the risk of explosion.

John Wilkins, UKAEA's head of site at Harwell, said: "Although with hindsight there was no real danger to the public, we put safety first by calling in the emergency services.

"We regret the inconvenience this caused to our friends and neighbours in the local community."

He added: "We recognise that in this case our monitoring of AEA Technology could have been more comprehensive.

"But we could not accept the implications that our actions put people at risk. The expert evidence we obtained confirmed there was no danger."

Judge Peter Crawford QC ordered UKAEA and AEA to pay their £4,000 fines within the next 14 days.