We served the prohibition notice straight away to stop this serious pollution

Colin Babb, Environment Agency

Environment Agency inspectors discovered the leak when they made an unannounced spot-check.

They noticed a strong smell coming from the plant in Brook Lane, Westbury.

Agency spokesman Mike Dunning said: "They should not have been able to smell it to anything like the extent they experienced."

Asked whether the smell should have been obvious to workers, he said: "One would have thought so."

Instant shutdown

A pollution filter system was not working and waste solvents - volatile organic compounds - were being released into the atmosphere at ground level.

Toxic emissions from the plant could contribute to low-level ozone pollution, similar to that caused by traffic fumes, said Mr Dunning.

Inspectors found ground-level pollution

The inspectors ordered an immediate shutdown of the affected area - meaning the whole factory had to close.

The company refused to comment on the incident.

Mr Dunning said: "They have to pinpoint the problem, bring in expert advisers to solve it, and demonstrate to the Environment Agency that they have taken the appropriate advice.

"Then they have a trial period while they operate the new system."

'Serious' leak

Only then can it be given back a licence for its solvent distillation and evaporation process.

Absolute Solvents took over the authorisation from the previous holder, Western Solvents, in December.

Colin Babb, an agency site inspector, said: "Absolute Solvents had been operating its plant without the necessary pollution control equipment.

"We served the prohibition notice straight away to stop this serious pollution.

"We are investigating the matter thoroughly and will consider all the factors before making a decision on further action.

"We are certainly not ruling out a prosecution."