THE Health and Safety Executive (HSE) has announced it will not prosecute power firm Enron over an explosion that killed three men.

The families of the men who died at the Teesside power station at Wilton, near Redcar, in August 2001, were told the news yesterday.

An HSE spokesman said: "Very careful consideration has been given to all the evidence surrounding this tragic incident.

"Taking into account the Health and Safety Commission's enforcement policy, the code for Crown Prosecutors and independent legal advice, the HSE has decided not to bring a prosecution following the investigation."

A four-day inquest held on Teesside in February recorded a verdict of accidental death.

But the HSE said its decision does not prevent any civil claim against the US company, which owned the plant at the time of the accident.

The three died after they were engulfed in a fireball while work was being carried out to adjust the voltage of a transformer.

Operations technicians Andy Sherwood, 36, of Hartlepool, and Darren Higgins, 28, of Normanby, suffered 100 per cent burns and died immediately after the accident on August 8.

Paul Surtees, 40, of Hawthorne, east Durham, suffered 90 per cent burns and died the following day.

A fourth man, Graeme White, 39, of Billingham, suffered ten per cent burns and is still receiving surgery.

The inquest heard that Mr Surtees, a maintenance manager, and Mr Higgins were attempting to adjust the voltage while the other two men were observing the unusual procedure.

The procedure would have enabled the men to close a circuit breaker to allow maintenance work elsewhere.

But the transformer was still receiving massive amounts of energy from a steam turbine.

A huge surge - enough to power five million electric fires - flooded into the transformer. Oil caught fire and flames burst out of the machine, engulfing the men.

Coroner Michael Sheffield told the jury they could record only a verdict of accidental death. He said that verdicts of corporate manslaughter or an open verdict would not fit with the evidence.

Safety managers at the plant later changed their procedures.