A spokesperson at the supplier, Kojima Industries said it appeared to be some kind of cyberattack. A spokesperson from Toyota described it as a "supplier system failure."
The incident might hurt Toyota's efforts to return to full production following factory halts in January and February because of chip shortages and COVID-related disruptions.
Toyota, which has remained relatively resilient to supply chain snags through most of the pandemic, has been trying to ramp up production to make up for lost output and meet soaring global demand for cars.
Toyota's production in January fell 15 percent from a year earlier, after it had to halt output in the Chinese city of Tianjin when the government carried out multiple rounds of mass-testing on residents.
Earlier this month, some of Toyota’s North American operations were affected by protests that shut some of the main trade routes between the U.S. and Canada.
The disruptions in the first two months of the year prompted Toyota to cut its output goal for the fiscal year through March to 8.5 million vehicles from a previous target of 9 million.
Toyota is investigating whether it can resume operations later this week, the Nikkei reported.
The automaker operates 28 assembly lines at 14 plants in Japan.
Bloomberg contributed to this report