INVESTIGATIONS were continuing today after a gas leak at one of Hampshire's biggest industrial sites resulted in thousands of residents being told to stay indoors.

Fawley refinery was at the centre of a major alert yesterday after hydrocarbon vapour began escaping from part of the huge petrochemical plant.

One worker was taken to hospital suffering from the effects of inhaling the fumes, and six others were treated on-site.

Police closed the Holbury section of the A326 Totton to Fawley road and warned residents to stay inside with their doors and windows shut.

Schools on both sides of Southampton Water were also urged to make sure that everyone was kept indoors.

Residents living opposite the refinery say that the area was hit by a nauseating smell after the leak occurred at 10.30am.

A Fawley spokesman confirmed that the 1,250-acre complex did not sound its alarm, which is supposed to warn residents if an incident is taking place.

He said: "We considered sounding the alarm, not because there was any danger to the public but because the smell was unpleasant. We didn't do so because the leak was isolated so quickly.

"Workers on-site were close to the source but by the time the vapour went off-site the concentration was much, much lower."

The spokesman said that an investigation would be held into the incident, which began when vapour leaked from a pipe and drifted towards the A326.

The Health and Safety Executive confirmed that it would be investigating the leak.

Coastguards were warned about the leak in case it had any implications for shipping in Southampton Water and the Solent.

A Coastguard spokesman said: "The wind was north-easterly, which means the vapour wouldn't have crossed the sea that much."

Schools caught up in the drama included Hamble Community College, where pupils stayed inside until the all-clear was given.

Ian Hoult, the county council's emergency planning officer, said: "There was a release from the site but it was quickly stopped and there was no threat to the public."

A police spokesman said: "Despite the unpleasant odour there was no danger to members of the public. However, if anyone feels they may have been adversely affected they are advised to consult their GP."

Eddie Holtham, chairman of Fawley Parish Council, said that it was the third incident at the refinery in the past few months.

In July, thick black smoke billowed from the site for more than 24 hours after a fire wrecked the equipment that injects steam into the flare stacks and dilutes the emissions.

Last month another problem at the refinery resulted in flares lighting up the night sky.