A major affiliate of Japan’s Toyota Motor Corp falsified emissions data on some engines as far back as 2003, more than a decade earlier than previously indicated, a company-sponsored probe showed on Tuesday.

The investigative committee tasked by automaker Hino Motors Ltd (7205.T) blamed the scandal on an environment where engineers did not feel able to challenge superiors, in a rare criticism of corporate culture in Japan.

The committee, composed of lawyers and a corporate adviser, was set up by Hino this year after it admitted to falsifying data related to emissions and fuel performance of four engines. Its findings, released on Tuesday, detail an inflexible atmosphere where it was difficult for staff to feel “psychological safety”, the committee said in a report.

A sense of past success on the part of management helped engender the culture, said committee chairperson Kazuo Sakakibara, who was the former head prosecutor at the Osaka District Public Prosecutors Office.

“The magnitude of their past successes has made them unable to change or look at themselves objectively, and they have been unaware of changes in the external environment and values,” he told a briefing.

“The organization has become an ill-organized one where people are unable to say what they cannot do.”

Hino’s president apologized to reporters and said management took its responsibilities seriously. The company said it would come up with a new corporate governance system within three months.

The automaker said the committee had found evidence of falsification stretching back as far as 2003, as opposed to the previously disclosed timeframe of around 2016.

The transportation ministry revoked the truck maker’s certification of the affected 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 (7261.T), Suzuki Motor Corp (7269.T) and Yamaha Motor Co Ltd (7272.T) had improperly tested vehicles for fuel economy and emissions.

Subaru Corp (7270.T) and Nissan Motor Co Ltd (7201.T) 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 (VOWG_p.DE) admitted it had installed secret software in hundreds of thousands of U.S. diesel cars to cheat emissions tests and that as many as 11 million vehicles could have similar software worldwide.