The world's largest automaker, Toyota Motor, will shut down its plants in Japan on Tuesday.
Japanese media such as the business newspaper Nikkei write of a hacker attack on a supplier.
Toyota itself spoke of a system collapse at the supplier Kojima Industries.
Patrick Welter
Correspondent for business and politics in Japan based in Tokyo.
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The first and second shifts would be canceled at the 14 Japanese plants.
Toyota is still checking whether it can resume production from Wednesday, writes Nikkei.
Kojima Industries manufactures plastic parts.
A spokesman for the company told Nikkei it was hit by "some kind of cyber attack."
The incident at the company appears to have caused malfunctions in a Toyota vehicle subsystem.
A one-day stop of the 28 lines in Japan costs Toyota a production loss of about 13,000 vehicles.
The interruption comes at a time when the automaker had to scale back its production target for the fiscal year ending in March to 8.5 million units due to a lack of supplies of semiconductors, among other things.