Mitsubishi Motors' woes got worse when the noted Japanese car maker admitted at a press conference recently that its cars' fuel tests have been rigged. And that this has been going on for over two decades.

In this latest development, Mitsubishi Motors' shares plunged when the news broke last Tuesday, according to The Guardian. The company said that its employees had improperly complied with Japanese regulations on the fuel-saving tests for 25 years.

The company also said that strictly high internal work compliance metrices may have implored its employees to exaggerate fuel efficiency values for its vehicles. Mitsubishi has already announced that it would do an independent investigation to determine further details surrounding the issue.

The company reportedly lost about half of its market shares following its admission to altering test results to four of the company's mini-car models. The company also said that two Nissan models were a part of the falsification fiasco.

Concerns were further raised when Mitsubishi added that more models may have been involved in the said tests. Critics and auto experts were quick to point out on the company's fate now that it would possibly face huge fines and compensation costs.

The company's R&D facilities have already been investigated by Japanese authorities. Because of the extent of the mishandling issue, even U.S. vehicle safety authorities have been asking for more information on the matter, as per the publication.

Mitsubishi also claims that proper testing methods were used on vehicles sold overseas and the U.S., according to Yahoo Finance. The company strongly contends that no data manipulation was made.

Apparently, the company had previously admitted to its non-compliance as of 2002. However, the recent disclosure actually went back as far as 1991. Tetsuro Aikawa, COO for Mitsubishi Motors, said he was completely unaware of the fuel economy rigging issue, and that he is especially worried that it is a problem why it was a hidden issue.

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