Two days after Mitsubishi revealed that employees manipulated mileage test data for 620,000 vehicles sold in Japan since 2013, U.S. regulators have opened their own investigation into the carmaker to find out if the same shenanigans occurred stateside.

Officials with the National Highway Traffic Safety Administration directed Mitsubishi to hand over any information on its vehicles sold in the United States, Reuters reports.

“We’ve requested information from Mitsubishi about this issue,” a spokesman for NHTSA said, declining to specify which models the agency sought data for.

For now, there’s no evidence that Mitsubishi cars in the U.S. include the same fuel inaccuracies as the 625,000 small cars sold in Japan, which included some vehicles manufactured for Nissan.

According to Mitsubishi tire pressure data was manipulated to make mileage appear 5% to 10% better than it actually was for 157,000 Mitsubishi eK wagon and eK Space light passenger cars, and 468,000 Dayz and Dayz Roox vehicles produced for Nissan Motor Co.

Mitsubishi president Tetsuro Aikawa apologized for the falsified data on Wednesday, noting that while he was unaware the irregularities were happening, he felt responsible, the Associated Press reports.

“The wrongdoing was intentional,” Aikawa said. “It is clear the falsification was done to make the mileage look better. But why they would resort to fraud to do this is still unclear.”

The falsified data was first spotted by Nissan when the company was assessing the current model in preparation for its next-generation vehicle.

“In response to Nissan’s request, Mitsubishi admitted that data had been intentionally manipulated in its fuel economy testing process for certification,” Nissan said.

Both automakers have stopped the sale of the so-called minicars, which are generally popular in the country for their great mileage, the AP reports.

U.S. auto safety regulator looking into Mitsubishi fuel economy issue [Reuters]

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