The Environmental Protection Agency has reached an agreement with Diamond Shamrock Chemical Co. requiring the firm to pay a $900,000 fine for failing to notify the government before manufacturing or importing three new chemicals.

The penalty against the Dallas firm is the largest ever collected under the "pre-manufacture notification" section of the Toxic Substances Control Act, the agency said.

Besides paying the fine, Diamond Shamrock agreed to conduct an audit at 43 facilities to assess compliance with the law, the EPA said. The agency will have the right to bring criminal enforcement actions or initiate court action for any violations the company might discover during the audit.

The EPA said the penalties against Diamond Shamrock were prompted by the company's voluntary disclosure last year that a wholly owned subsidiary, Duolite International Inc., had manufactured or imported three chemicals without notifying the agency as required by law.

The chemicals were not identified because the firm considers their names confidential under terms of the law, the EPA said.

Ken Haseley, a Diamond Shamrock spokesman in Dallas, said the actions by Duolite, now a former subsidiary, were technical violations of the law that did not threaten human health or the environment.