Mitsubishi Motors has been told to stop selling eight more models after it was found they overstated fuel efficiency.
The investigation by the transport ministry comes after the firm admitted in April to falsifying the fuel efficiency of two of its models, along with two cars produced for Nissan.
The admission led to a suspension of sales of the vehicles, prompting a sharp drop in the firm's market value.
Nissan subsequently bought a controlling stake in the company.
The latest models affected by the fuel efficiency scandal include variants of the Pajero, Outlander and RVR SUV cars.
The models in the initial scandal were two minicars sold under the Mitsubishi brand, and two other similar models the company built for Nissan.
"Our investigation confirmed that the fuel economy on eight models were as much as 8.8% and on average 4.2% lower than advertised," the transport ministry said in a statement.
The ministry ordered the carmaker to stop selling those eight models on the domestic market while it submitted correct readings.
In the wake of the initial scandal in April, some $3bn was wiped off the carmaker's market value. In May, fellow carmaker Nissan moved in to take a 34% controlling stake in the company in a 237bn yen ($2.2bn; £1.52bn) deal.
In April, Mitsubishi Motors admitted it had rigged tests for the past 25 years.
Regulations changed in 1991 to reflect stop-start urban driving more accurately, but Mitsubishi failed to heed the change.
In May, the firm's president, Tetsuro Aikawa, stepped down.
Mitsubishi Motors also forecast a huge loss in the wake of the scandal, saying in June it expected a net loss of 145bn yen for the current business year.
The expected loss marks the first fall in profit for the car firm since the 2008 financial crisis.
Before the fuel rigging came to light, the carmaker was the sixth biggest in Japan and the 16th largest worldwide.