Shares in Mitsubishi Motors fell by their largest amount in more than a decade following the release of an official statement saying it has found evidence that its employees have falsified emissions test data for several models of vehicles.

The Japan based manufacturer of the hugely popular Lancer, Pajero and Outlander vehicles identified that fuel consumption testing data submitted to the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) was researched improperly.

The admission by Mitsubishi states that employees conducted improper testing to present falsified fuel consumption and emissions testing data, rather than factual data, and that their researcher’s methods differed from those required by Japanese law.

The cars in question are four mini-car models, the eK Wagon, eK Space, Dayz, and Dayz Roox which have been manufactured by Mitsubishi and supplied to Nissan Motors Corporation since June 2013.

As of March 2016, Mitsubishi had already sold 157,000 units of the eK Wagon and eK Space and supplied 468,000 units of the Dayz and Dayz Roox to Nissan.

The problem was found after Nissan pointed out inconsistencies in fuel consumption and emissions testing data. This prompted Mitsubishi to conduct an internal probe, and supported Nissan’s case that fuel-emissions data was falsified after initially finding deviations in research figures.

According to a recently published article by Kyodo News, Mitsubishi falsified their fuel-emissions test data by manipulating the load placed on the tyres of four different models in order to make their fuel economy appear more efficient.

In response to the scandal, Mitsubishi have halted production and sales of the models in question. Nissan has also ceased selling the models in question and are yet to publish a compensation plan to resolve the issue with corporate stakeholders and customers.

Other models manufactured by Mitsubishi for the Japanese domestic market are also under investigation, and will therefore be subjected to the same fuel emissions testing required by Japanese law.

Mitsubishi has commissioned a panel consisting of external experts to investigate and resolve the matter, and have stated that they will publish the results of their investigation as soon as it is complete.