Mazda, Toyota, and Nissan are among those affected.
Several car manufacturers have launched investigations after supplier Kobe Steel admitted falsifying data for some of its aluminum and copper products. The company confirmed that almost 39,000 tons of aluminum rolls and forgings shipped between September 1, 2016 and August 31, 2017 were affected by what it called "improper conduct."
A statement from the firm reads: "A portion of the products traded with customers did not comply with the product specifications which were agreed between the company and its customers. Data in inspection certificates had been improperly rewritten, and the products were shipped as having met the specifications concerned."
Toyota, Nissan, Subaru, and Mazda have all confirmed that they are customers of the metal producer and are currently working to find out which vehicles are affected. Honda, Ford and Suzuki are also reported to be among Kobe Steel's customers.
Subaru admitted that it used Kobe Steel products in both its cars and aircrafts, and that it was "working rapidly to identify which parts, vehicle models, and planes are subject to the matter."
A Mazda spokesperson said: "With the safety and peace of mind of our customers as our highest priority, we will continue gathering information and quickly investigate the impact on vehicle quality while investigating what actions to take moving forward."
Toyota, meanwhile, released a statement that read: "Our priority in everything we do is the safety of our customers and we are rapidly working to identify if any of our vehicle models may potentially be affected, and via which components.
"At the same time, we are considering what measures need to be put in place going forward to address this matter. Toyota has long requested its suppliers to be thorough in matters related to compliance. We recognise that this breach of compliance principles on the part of a supplier is a grave issue."
Nissan confirmed that it used Kobe Steel’s aluminium in vehicle hoods and doors, but said it was "working to quickly assess any potential impact on vehicle functionality."
Kobe Steel said it would work with its customers to ascertain "the impact of the nonconforming products on quality (including safety) of the end products." The company has also commissioned an independent law firm to investigate the scandal.