AUSTIN, Texas -- A company that operates gas stations in several states, including Colorado, has caught the attention of Texas officials, who claim the company is ripping off drivers at the pump.

Authorities say a weekend investigation found 990 pumps were rigged to favor Petroleum Wholesale by as much as one-tenth of a gallon for every five gallons sold. Pumps in violation were immediately shut down by Texas inspectors.

The company operates stations under the name Sunmart.

Texas Agriculture Commissioner Todd Staples said he suspects the pumps were intentionally tampered with to deliver less gasoline than they were supposed to. He said it's not unusual for pumps to be slightly inaccurate, but the pattern of discrepancies at Sunmart stations was beyond the norm.

The investigation found that, across Texas, 990 of Sunmart's 1,704 fuel pumps were cheating consumers.

Petroleum Wholesale also operates gas stations in Oklahoma, Kansas, Utah and Arizona.

Authorities have not uncovered any violations in those states, but Staples said he has notified officials of his findings.

Sunmart operates six gas stations in Colorado and only one has received a complaint, said Bill Thoennes with the Colorado Department of Weights and Measures. He said the complaint at the Sunmart station in Golden, Colo., was resolved late last year.

Colorado checks gas pumps once every 18 months and also conducts random checks of gas stations' calibration equipment, Thoennes said.

Investigators check equipment that has a seal on it that only a person from Weights and Measure would be able to open. When this seal has been tampered with, investigator red flag that pump, he said.

Thoennes said when investigators do find a pump that is not calibrating correctly, it is usually due to wear and tear on the machine, and not from deliberate fraud.