Japanese automaker Mitsubishi Motors admitted that it falsified fuel-efficiency data on 625,000 vehicles.
Mitsubishi president Tetsuro Aikawa bowed in apology during a news conference Wednesday in Tokyo admitting to the irregularities.
The company said the false data dates back to 2013, involving its eK mini-wagon and eK Space light passenger cars, as well as it Dayz Roox vehicles it produces for rival carmaker Nissan Motors. The problem was uncovered after Nissan noticed the inconsistencies in the data, prompting Mitsubishi to conduct an internal probe.
Aikawa said the tire pressure tests on the vehicles were rigged to make the fuel mileage 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," he said.
The news sent shares in the world's sixth-largest automaker plunging 15 percent in Wednesday's trading session.
Aikawa told reporters the company will stop selling the vehicles, and will conduct an investigation to determine if fuel efficiency data was altered in vehicles sold internationally.
Mitsubishi is the second carmaker accused of falsifying environmental data over the past year. Germany's Volkswagen admitted late last year that it installed software on millions of its vehicles that activated bogus emissions controls to deceive testing officials.
The Japanese automaker is no stranger to scandal, nearly going out of business after admitting back in 2000 that it covered up major safety defects for several decades.