Japan's Kobe Steel has increased the number of firms it says have been affected by its data fabrication scandal from 200 to 500.
It also said it had found "inappropriate actions" relating to nine more products, including falsifying data.
Earlier this week, Kobe admitted falsifying quality data on some of its products for up to a decade.
The news has wiped out about $1.8bn off Kobe Steel's market value this week.
More than 30 non-Japanese customers, including Daimler and Airbus, have been affected by the firm's data fabrication, Japan's Nikkei newspaper reported on Friday.
Airbus said it did not buy products directly from Kobe Steel, but that it was investigating its supply chain.
"So far we have not identified any suppliers that procure materials from Kobe Steel for parts fitted on our aircraft," a spokesman said.
An internal investigation at Kobe Steel found 70 cases of data tampering at its Kobelco Research unit.
Manufacturer such as General Motors, Boeing and Toyota have been investigating whether they have used any of the sub-standard materials from Japan's third-largest steel maker.
Boeing, has used Kobe Steel products that include those falsely certified by the Japanese company, Reuters reported.
The world's biggest maker of passenger jets does not consider this a safety issue, but the revelation may raise compensation costs for the Japanese company, the news agency said.
Central Japan Railway has said some Kobe Steel parts for its bullet trains did not meet Japanese industrial standards, but there were no safety issues.
Hitachi said its new trains in Britain used Kobe Steel, but had all passed rigorous tests.
Mazda and Honda have both said they have used Kobe aluminium in some car bonnets.