DETROIT — Ford has launched an investigation into whether it overstated gas mileage and understated emissions from a wide range of vehicles.

The company says that in September, a group of employees reported possible problems with a mathematical model used to calculate pollution and mileage, prompting the company to hire an outside firm to run tests.

Testing will start with the 2019 Ford Ranger small pickup truck, and if problems are found, the company will start looking at models dating to 2017.

Ford says it has no evidence yet that mileage or pollution numbers are wrong, but the investigation has just started. The company says it’s too early to tell how many and which models might be involved.

Depending on what is found, Ford could be required to restate the mileage on EPA-approved window stickers as well as reimburse owners for the mileage difference. The company could also face penalties from the government agencies.

“At Ford, we believe that trust in our brand is earned by acting with integrity and transparency,” Kim Pittel, the company’s vice president for environment and safety engineering, said Thursday.

The U.S. Environmental Protection Agency and the California Air Resources Board, which monitor emissions and mileage, have been informed of the probe, according to the company. The EPA said that Ford disclosed the issues on Tuesday.

“The investigation is ongoing and the information is too incomplete for EPA to reach any conclusions,” the agency said. “We take the potential issues seriously and are following up with the company to fully understand the circumstances behind this disclosure.”