TOKYO—Mitsubishi Motors Corp. on Wednesday posted a $174 million special loss and warned that related costs could balloon further as it grapples with the fallout from a fuel economy testing scandal that has led to the resignation of its president.

Mitsubishi's sales are declining and its costs are rising after it first admitted in April to falsifying data related to fuel economy to make mileage look better on four models, so-called minicars sold only in Japan. Two of these minicars, with 0.66 liter engines, were manufactured by Mitsubishi and sold under Nissan Motor Co.'s brand name.

Mitsubishi had originally reported a ¥ 89 billion net profit for the year ended March 31. But in light of the special ¥ 19 billion ($174 million) loss, it said it was revising that figure to a ¥ 73 billion net profit—an unusual case of a company revising its reported results for a period that is already over.

Scandal-related costs could increase further down the road, as the company said it has "estimated part of losses based on internal examination results" on the four minicars.

Mitsubishi has also said that data manipulation took place beyond minicars, in some versions of its Pajero and RVR sport-utility vehicles in Japan.

None of its vehicles sold overseas are affected by the mileage problem, Mitsubishi has said.

The scandal broadened last week to include another of Japan's second-tier auto makers, Suzuki Motor Corp., which has also admitted to improperly testing its vehicles.

Mitsubishi and Suzuki are among several global auto makers under scrutiny after Volkswagen AG late last year said it used illegal software on some of its diesel-powered vehicles to cheat on U.S. emissions tests.

Earlier this month Nissan agreed to take a 34% controlling stake in Mitsubishi Motors for more than $2 billion, subject to regulatory approval. It said it would help Japan's sixth biggest auto maker by global sales volume rebuild its damaged brand image.

As part of the deal, Nissan will send in an executive, Mitsuhiko Yamashita, to head vehicle development at Mitsubishi Motors, Mitsubishi said Wednesday. The company has also said its president Tetsuro Aikawa will step down.

The company's shareholders will vote on the personnel changes at the company's annual meeting on June 24.

Write to Megumi Fujikawa at megumi.fujikawa@wsj.com

(END) Dow Jones Newswires

May 25, 2016 06:05 ET (10:05 GMT)