Following a government ordered investigation, Subaru has determined employees improperly altered fuel economy and emissions data.

According to the automaker, “certain measurements and data were inappropriately altered” during final vehicle inspections at the Gunma and Yajima plants. The company believes the issue only affected 903 vehicles which were built between December 2012 and November 2017. Subaru says it couldn’t find data from measurement equipment prior to 2012 but it believes there is a “high probability that such manipulation of fuel economy and emissions data commenced around 2002.”

The fuel economy and emission alterations were reportedly made by factory-floor inspectors and foremen. The methods for altering the data were passed from senior inspectors to junior inspectors but Subaru says employees weren’t instructed to do this. The automaker goes on to say some group chiefs were likely aware of the altered data but “managers at, or above, the section chief level and executive managers were not aware of alterations.”

Subaru presumes there were three key motivations for altering the data. The first is that senior inspectors ordered other inspectors to adjust fuel economy and emission figures for sample vehicles that did not meet standards.

Even vehicles that did meet internal quality control standards were subject to alterations as “inspectors altered measurement values with the intention of reducing variance in measurement values in order to avoid questions from the group chiefs and the section chief on such variance.” The company notes alterations were made to make the results look better and worse that what they actually were.

Subaru noted a third possible reason for the manipulation might have been inadequate training and deficient internal rules. As the company explains, in certain cases the measurement values can legally be altered to account for errors in measurement equipment and some inspectors might have misunderstand how to do this.

The company says its internal quality control standards are stricter than required so no recall will be needed. However, the company says employees engaged in “inappropriate conduct” and this caused an “extremely serious compliance problem.”

Subaru says they sincerely regret what happened and issued its “deepest apologies for the significant trouble and inconvenience caused to our customers, partners, and all other stakeholders.”