TOKYO—Toyota Motor Corp. said it would shut down all 14 of its factories in Japan on Tuesday after a supplier had a computer problem.

The supplier, Kojima Industries Corp., said it believed the problem stemmed from a cyberattack or possibly a malicious email with a virus, but it said the exact cause wasn’t known. Kojima, a supplier of plastic parts for car interiors, said it shut down its servers to prevent the problem from spreading, and its website was down.

A…

TOKYO—
Toyota
Motor Corp. said it would shut down all 14 of its factories in Japan on Tuesday after a supplier had a computer problem.

The supplier, Kojima Industries Corp., said it believed the problem stemmed from a cyberattack or possibly a malicious email with a virus, but it said the exact cause wasn’t known. Kojima, a supplier of plastic parts for car interiors, said it shut down its servers to prevent the problem from spreading, and its website was down.

A Toyota spokesman said the car maker didn’t know yet whether the Japan factories would stay closed beyond Tuesday because it was still assessing the problem.

The shutdown is the latest problem to hit Toyota’s production after a global semiconductor shortage forced factories to operate below full capacity for much of the past year.

The company said in February that it expected global production of Toyota and Lexus vehicles to total 8.5 million vehicles in the year ending March 2022, down from a production forecast of nine million vehicles issued in November.

Japanese factories represent roughly a third of Toyota’s annual production.

Write to Sean McLain at sean.mclain@wsj.com