A CEMENT factory has been cautioned by the Environment Agency after it was found to have released more than three times the recommended limit of potentially poisonous metals into the air.

And the shock findings come just months after Castle Cement's Ribblesdale plant was told by the Government agency to carry out at least two environmental patrols each day to monitor these emissions.

The formal warnings were issued by the Environment Agency to Castle Cement's plant this week, over breaches of the Clitheroe factory's operating licence earlier in the year.

The licence, granted by the agency to control the emissions the plant produces, includes limits on the amounts of 'group three' metals the factory can release from two of its kilns. These toxic metals include arsenic, chromium, cobalt, copper, lead and tin.

The agency found that the plant, which employs more than 300 people, broke rules set out in the Environmental Protection Act. In February of this year, emissions from the plant contained an average of 0.98mg/m3 of group three metals. The limit is just 0.5mg/m3.

The second breach came in April when emissions contained 1.7mg/m3 -- more than three times the limit. But the concrete factory failed to report the findings to the Environment Agency, breaching its operating licence for a third time.

Steven Zdolyny, the Environment Agency's Regional Solicitor, said: "The agency views these issues very seriously. We carried out a thorough investigation to determine what happened, resulting in these formal cautions, together with an Enforcement Notice and warning letter."

For each of the breaches the company has received a caution, and the agency has also served it with a legally binding Enforcement Notice. The notice requires the firm to take steps to control its emissions, and report any further breaches immediately.

The Environment Agency say that while the metals released are potentially poisonous, they are well below the levels which could harm the environment.

But Steven Zdolyny added: "Castle Cement has been warned that stronger enforcement action, including a possible prosecution, may be taken by the Environment Agency if there are any further breaches of its authorisation."

The company has hit back at the findings, suggesting they are from an error in the testing process. A spokesman for Castle Cement Limited, based in Birmingham, said: "We accept the Environment Agency's findings, but believe that the release of the group three metals has been controlled at all times during 2001.

"Castle Cement is firmly of the belief that the values measured on the days in question were due to errors during the sampling procedure which led to a contamination of the samples by particles inside the sampling port."