BELLEVILLE, Mich. -- A Belleville gas station has been fined for charging customers for mid-grade fuel when they were getting regular gas, according to state officials.

The Budget Fuel Citgo station at 496 Main St. in Belleville and the petroleum transport company that delivered the gas have both been fined for the mislabeled gasoline after a former employee alerted regulators.

Scott Francis of Ypsilanti, a former employee of the gas station, said he noticed the delivery truck putting the lower grade gas into the mid-grade storage tank on several occasions, which is a violation of the Motor Fuels Quality Act.

Francis said he talked to the station's owner, whom he identified as Woody Sloan, several times about the situation, and eventually was told in mid-March to be gone by the time the owner got back from a vacation.

Victoria Sloan, the owner of the gas station, said it is the transport company's fault.

Buz Sloan, part owner of Sloan Petroleum Transport, denied they were at fault.

The Ann Arbor News confirmed the parties involved are related, but could not confirm how.

The state said it had been taking place for three months, from January to March, and the holding tank had been filled up at least 23 times.

According to a state report, the mid-grade octane gas price was set at $3.36 a gallon, but tests revealed the gasoline was really regular octane and should have been set at a regular price of $3.29.

The station collected the 7-cent difference from thousands of unsuspecting customers'.

One customer said they wondered why the stations gas prices were always lower than their competitors.

And the station's owner said that's her explanation. She said no customers were ever cheated, because she sold gas cheaper than most other stations.

The gas station owner was fined $2,740 and has until Thursday to either pay the fine or appeal it. The transport company was fined $12,911 and has until May 2 to pay or appeal.