Car giant Toyota on Wednesday blamed a shutdown of all its factories in Japan last month on a system malfunction caused by "insufficient disk space".

The world's top-selling automaker said the one-day stoppage on August 29 at all 14 of its domestic plants happened after servers that process parts orders broke down following a maintenance procedure.

During this operation "data that had accumulated in the database was deleted and organised, and an error occurred due to insufficient disk space, causing the system to stop", Toyota said in a statement.

The firm also confirmed its earlier preliminary finding that the incident was "not caused by a cyberattack".

Toyota is famous for its "just-in-time" production system of providing only small deliveries of necessary parts and other items at various steps of the assembly process.

This practice minimises costs while improving efficiency and is studied by other manufacturers and at business schools around the world, but also comes with risks.