Mitsubishi Motors Corp. said Wednesday says it found evidence its employees intentionally falsified fuel mileage test data for several models of vehicles.

The Tokyo-based automaker said Wednesday that the inaccurate tests involved 157,000 of its own-brand eK wagon and eK Space light passenger cars, and 468,000 Dayz Roox vehicles produced for Nissan Motor Co. All vehicles included have been produced since mid-2013.

Worldwide, Mitsubishi sold about a million vehicles last year.

The problem was found after Nissan pointed out inconsistencies in data, the company said. Mitsubishi conducted an internal probe and found that tire pressure data was falsified to make mileage appear better than it actually was.

"The wrongdoing was intentional. 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," company president Tetsuro Aikawa told reporters.

Panel being set up to investigate improper fuel economy tests 0:39

He and other company executives bowed in apology.

Aikawa said that although he was unaware the irregularities were happening, "I feel responsible."

The company said it would investigate whether data were altered for vehicles sold overseas.

Doubt cast on entire industry

Nissan said in a statement that it recently discovered discrepancies in data from Mitsubishi about light vehicles it provided while 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.

It said that after consulting the Japan's transport ministry, it told dealers to stop selling the affected vehicles. Nissan was considering ways to help owners of the cars already sold.

"Nissan understands and regrets the inconvenience and concern this will cause our valued customers," the company said.

Mitsubishi Motors struggled for years to win back consumer trust after an auto defects scandal in the early 2000s over cover-ups of problems such as failing brakes, faulty clutches and fuel tanks prone to falling off dating back to the 1970s.