By Satoshi Sugiyama

TOKYO (Reuters) -Japan's Hino Motors Ltd falsified emissions data on some engines as far back as 2003, a committee tasked by the automaker said on Tuesday, blaming a culture where engineers were not able to challenge senior staff.

The committee was set up by the Toyota Motor Corp unit after it admitted this year to falsifying data related to emissions and fuel performance of four engines. Its findings cast a harsh light on the culture of the automaker.

That internal culture made it easy for power harassment to happen and difficult for staff to feel psychological safety, the committee said in a report.

The automaker said the committee had found evidence of falsification stretching back as far as 2003, at least a decade earlier than previously expected.

The transportation ministry revoked the truck maker's certification of those engines in March.

Hino has recalled close to 47,000 vehicles made between April 2017 and March this year, but the recall is likely to widen, the Nikkei business daily reported on Tuesday.

Toyota owns 50.1% of Hino. Shares of Hino fell almost 10% on Tuesday.

Hino has joined a string of Japanese automakers involved in improper emissions tests.

In 2018, the government said Mazda Motor Corp, Suzuki Motor Corp and Yamaha Motor Co Ltd had improperly tested vehicles for fuel economy and emissions.

Subaru Corp and Nissan Motor Co Ltd were under scrutiny for the same reason the year before.

The accuracy of automakers' emissions data was thrown into doubt in 2015 when Germany's Volkswagen AG admitted that it had installed secret software in hundreds of thousands of U.S. diesel cars to cheat exhaust emissions tests and that as many as 11 million vehicles could have similar software installed worldwide.

(Reporting by Satoshi Sugiyama; Editing by David Dolan and Christopher Cushing)