Toyota said on Tuesday it was uncertain when production would resume at 14 plants in Japan after an apparent cyber attack affected a supplier.

The automaker had said earlier it would suspend domestic factory operations today, losing around 13,000 cars of output, after a supplier of plastic parts and electronic components was hit by a suspected cyber attack.

Toyota described the issue as a “system malfunction”.

Kojima Industries, a Toyota tier-1 supplier of exterior and interior body parts, said it had detected an unexplained error in its computer server system which prevented it from communicating with Toyota and from monitoring production even though there was nothing physically wrong with the production equipment.

Kojima spokesman Tomohiro Takayama said: “This has never happened before. We are not sure yet if it is a cyberattack, but we suspect it might be one”.

The company was not sure when the problem would be fixed so production could resume.

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Toyota apologised for the inconvenience to its customers and vowed to fix the problem as soon as possible.

Its truck subsidiary Hino Motor and small car subsidiary Daihatsu Motor also halted production due to the software malfunction.

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