Toyota has blamed a recent shutdown of all of its factories in Japan on a system malfunction caused by “insufficient disk space”.

The Japanese carmaker said the stoppage on 29 August at all 14 of its domestic plants occurred after servers that process orders for vehicle parts broke down following a maintenance procedure carried out the previous day.

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 on Wednesday.

The world’s top-selling automaker reiterated that the incident had not been caused by a cyber-attack. “We would like to apologise once again to our customers, suppliers, and related parties for any inconvenience caused by the suspension of our domestic plants,” it said.

Toyota said the system had been restored after the data was transferred to a server with a bigger capacity, enabling it to restart production at the plants – which together account for about a third of the automaker’s global production – the following day.

“We will review our maintenance procedures and strengthen our efforts to prevent a recurrence, so that we can deliver as many vehicles to our customers as soon as possible,” it added.

Toyota is known for its “just-in-time” production system of providing only small deliveries of necessary parts and other items at various stages of the assembly process.

This minimises costs and improves efficiency, and is studied by other manufacturers and at business schools around the world. However, as last month’s technical glitch proves, it comes with risks.

Toyota had to shut down the same 14 factories for a day in February last year when one of its suppliers said one of its file servers had been infected with a virus, raising questions about the cybersecurity of Japan’s supply chains.