Prosecutors and police raided offices of Kobe Steel Ltd. in Kobe, Tokyo and other locations Tuesday over a data fabrication scandal that has rocked the Japanese manufacturing industry.

Authorities believe the company violated a law that prevents unfair competition by systematically misrepresenting its products.

In addition to the firm’s main Tokyo office, the authorities also raided the company’s headquarters in Kobe as well as three manufacturing plants.

“We are dealing seriously with the investigation,” an official with the company’s public relations division said.

Kobe Steel has admitted to falsifying quality inspection data for aluminum and copper products, which have been supplied to over 600 companies at home and abroad, and used in cars, aircraft, space rockets and defense equipment.

According to the company’s final report on the scandal, released in March, the steel-maker altered data regarding strength and other material properties at 23 domestic and overseas plants to make its products appear as if they met client specifications.

Kobe Steel said about 40 employees were involved in the irregularities, including former board members. Data had been fabricated since around the 1970s at its plant in Tochigi Prefecture, according to the company.

The prosecutors had already begun a probe into the fabrication of Kobe Steel’s quality data and the firm had voluntarily submitted related documents. But prosecutors judged that the search was necessary to back up the claimed misconduct.

If found guilty, individuals could face prison terms of up to five years or fines of up to ¥5 million — or both — while the corporation could face a fine of up to ¥300 million.

Major Japanese carmakers including Toyota Motor Corp. and Honda Motor Co. have said they used Kobe Steel products in their vehicles. Affected products have also been used by Central Japan Railway Co. for shinkansen and Mitsubishi Heavy Industries Ltd. for Mitsubishi Regional Jet passenger planes.

The companies have said the falsified data do not pose safety issues for the products.

The U.S. Justice Department has separately launched a probe into the case, asking the steel-maker to submit documents linked to the scandal.

Customers in the United States and Canada have filed class-action lawsuits seeking compensation for the use of substandard products manufactured by the company.