A company statement says the theft occurred Tuesday at the El Gallo 1 mine and involved 900 kilograms (1,984 pounds) of gold-bearing concentrate containing approximately 7,000 ounces of gold.
The company said yesterday that the crime was being investigated by Mexican authorities.
It said its insurance policies will not be enough to cover the losses. The statement said no one was injured and mining operations were not affected, but did not provide any more details about the robbery.