A GOVERNMENT investigation was under way last night into a radiation alert that led to a name check of 850 workers from a North-East power plant.

The alarm was raised after more than 440 gallons of radioactive water spilled from a broken pipe at Hartlepool nuclear power station.

Police and 13 fire engines stood by while on-site experts isolated the contaminated area and made it safe.

Cleveland Police and Cleveland Fire Brigade said the leak had been contained on site and the public had not been endangered. The one working reactor at the station remained operational.

An internal British Energy inquiry began immediately after the alert, at about 2pm yesterday.

The Environment Agency and the Nuclear Installation Inspectorate, a division of the Health and Safety Executive, will also investigate and make their own independent report.

What caused the pipe to break had not been established yesterday.

More than 850 staff gathered at a prescribed site at the power station to be accounted for while experts made the area safe.

Cleveland Fire Brigade sent ten engines, two from Stockton, two from Thornaby, two from Billingham, and four from Hartlepool.

The brigade also sent its specialist environment protection unit and an emergency tender and a support vehicle from its headquarters, in Hartlepool.

A spokesman for British Energy said the contaminated, or "tritiated" water, was a by-product of the plant.

He said: "There were no off-site leaks and although all the staff were mustered that was merely a standard procedure.

"The same safety practices apply for small incidents as major ones. There was no question of the public being in danger at any point."

However, Geoff Lilley, administrative co-ordinator for the Hartlepool and North Tees Friends of the Earth group and a Greenpeace activist, said the leak was worrying.

"It is a very well-known fact that there is no such thing as a safe leak of radioactive waste," he said. "If 440 gallons of contaminated water has been released that is bad for the environment, no matter how they spin it.

"It shows that accidents do happen and at a nuclear power station they can be catastrophic."

A spokesman for Greenpeace said: "British Energy has had to close reactors in the North-West plants of Heysham and Sizewell in the last 12 months.

"With incidents like this it can hardly assure the public, which is still subsidising this supposedly privatised industry with millions of pounds every year."

A police spokesman said: "The leak has been confined to a building on the site and there are no off-site implications.

"There were no casualties, the leak was sealed and the affected area cleaned up."

The Environment Agency confirmed it would be working closely with the Nuclear Installation Inspectorate on the investigation.