SACRAMENTO, Calif. (AP) –– State regulators have opened a workplace safety investigation at a Northern California plastics factory where a fire raged a day earlier.

Investigators with the California Division of Occupational Safety and Health began looking into practices at Macro Plastics Inc. on Wednesday. An initial investigation suggested that Tuesday’s inferno, which sent black smoke billowing into the sky, was caused by an employee working with open flame in a storage area.

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No injuries or building damage were reported.

Cal/OSHA spokeswoman Erika Monterroza says the agency wants to be sure workers were following safety regulations.

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Macro Plastics makes bins used for harvested grapes and other agricultural products. The fire was behind the company’s headquarters in Fairfield, midway between Sacramento and San Francisco.

Numerous telephone messages left Wednesday for plant officials were not returned.

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