Toyota said Wednesday the computer system failure that resulted in a suspension of operations at all 14 of its group's vehicle assembly plants in Japan late last month was the result of a server malfunction error.
The problem occurred after data was collected during part of normal system maintenance work on Aug. 27, the company said.
A similar failure occurred in the backup function, which led to a halt of operations at its factories, it said.
Toyota said that it had confirmed that the malfunction was not caused by a cyberattack.
"We will review our maintenance procedures and strengthen our efforts to prevent a recurrence," the company said in a statement.
Toyota's domestic production ground to a halt on Aug. 29 after the system that makes parts orders failed. The company transferred the data to a server with a larger capacity and restarted production the next day, it said.