AUSTIN—Texas drivers who recently bought gas at hundreds of Sunmart stations probably were shortchanged, according to results of a state investigation released Tuesday.

A weekend investigation found 990 pumps were rigged to favor Petroleum Wholesale, which operates gas stations under the name Sunmart, by as much as one-tenth of a gallon for every five gallons sold. Pumps found to be in violation were immediately shut down by state inspectors.

“I strongly suspect this was an intentional act,” said Texas Agriculture Commissioner Todd Staples, whose office is charged with checking fuel pumps. Attorney General Greg Abbott’s office is investigating, Staples said, noting that his office could fine the company as much as $100,000.

A call to The Woodlands-based company seeking comment was not immediately returned Tuesday.

Staples said his office began investigating Friday, after noticing a spike in violations. It’s not unusual for pumps to be slightly inaccurate, but Staples said the pattern of discrepancies found at Sunmart stations were beyond the norm.

“I believe the facts would have been even more incriminating had the company not dispatched a band of technicians scurrying to get ahead of my team of inspectors in order to recalibrate faulty fuel pumps,” Staples said.

Across the state, 990 of Sunmart’s 1,704 fuel pumps were found to be cheating consumers, according to the investigation.

Sunmart, the operating name for Petroleum Wholesale, also operates gas stations in Oklahoma, Kansas, Colorado, Utah and Arizona. Staples said he has alerted officials in those states to his findings.

“At a time when families are struggling to purchase fuel, I am sure that all Texans would agree with me that despicable violations such as these are repulsive and must be prosecuted to the fullest extent of the law,” Staples said.