WASHINGTON (Reuters) - The U.S. Environmental Protection Agency said on Tuesday it ordered Mitsubishi Motors Corp (>> MITSUBISHI MOTORS CORPORATION) to provide additional information and conduct new tests of U.S. vehicles after the Japanese automaker's admission that it did not properly follow fuel economy test procedures in Japan since 1991.

Mitsubishi said earlier on Tuesday that it used fuel economy testing methods that did not comply with Japanese regulations for 25 years, much longer than previously known.

EPA spokeswoman Laura Allen said the agency has instructed Mitsubishi to "provide additional information regarding their U.S. vehicles. The agency will be directing the company to conduct additional coast down testing for vehicles sold in the U.S."

Mitsubishi, Japan's sixth-largest automaker, has lost half its market value, some $3.9 billion (2.7 billion pounds) , since it admitted last week to manipulating test data for four domestic mini-vehicle models, including two it produced for Nissan Motor Co (>> Nissan Motor Co Ltd).

An EPA spokeswoman declined to say if the agency suspects Mitsubishi of wrongdoing in the United States or if EPA plans to conduct its own testing.

The U.S. National Highway Traffic Safety Administration said last week it is also seeking information from Mitsubishi. NHTSA Administrator Mark Rosekind said on Friday that the Mitsubishi issue "is brand new. So right now we're just collecting data."

In 2015, Mitsubishi sold 95,342 vehicles in the United States, up 22.8 percent, accounting for 0.5 percent of U.S. auto industry sales, according to Autodata Corp. Mitsubishi U.S. sales are up 6 percent in the first three months of 2016.

In Japan, Mitsubishi said aggressive internal targets may have put pressure on employees to overstate the fuel economy of its vehicles, and that it would set up an external committee to investigate the matter.

Mitsubishi has also said that more models may have used tests noncompliant with Japanese standards, prompting concern about ballooning potential compensation costs and fines. Japanese authorities have raided one of the company's research and development facilities.

Mitsubishi said on Tuesday it used appropriate testing methods on vehicles sold in the United States, and had no indications of data manipulation in vehicles sold in other overseas markets. A spokesman for Mitsubishi North America could not immediately be reached for comment.

(Reporting by David Shepardson; Editing by Steve Orlofsky and Matthew Lewis)

By David Shepardson

Stocks treated in this article : MITSUBISHI MOTORS CORPORATION, Nissan Motor Co Ltd