TOKYO — A malfunction that shut down all of Toyota Motor Corp.’s plants in Japan on Tuesday happened during an update of the automaker’s parts ordering system, two people with knowledge of the matter told Reuters.

The world’s top-selling automaker has not given any details of what went wrong to cause the closure and a company spokesperson on Wednesday was unable to say whether the glitch happened during a system update.

Toyota, which restarted operations at its Japanese assembly plants on Wednesday, has seen production recovering this year. The full-day outage at its domestic plants could be equivalent to $356 million in revenue, Reuters calculations based on output data and financial reporting showed.

The company said its global sales had risen 8 percent in July from the same month a year earlier to a record 859,506 vehicles. It also reported a 15 percent increase in global production in that month.

The automaker has now posted year-on-year increases in global sales for six straight months, and production increases for seven, highlighting its recovery from last year’s supply chain snarlups and COVID-19 containment measures.

Both figures include Toyota’s Lexus luxury brand.

Sales in China fell 15 percent in July, contrasting with stronger sales in Japan, the U.S. and Europe. Domestic sales rose 35 percent and those in the U.S. increased by 8 percent.

Numbers for August — which will not be available until next month — are likely to be hit by Tuesday’s output suspension.

Toyota’s global production is likely to reach around 10.2 million vehicles this year, topping 10 million for the first time, Nikkei reported late on Wednesday. Toyota declined to comment on the projection.

The company continues to investigate the cause of Tuesday’s plant malfunction, but has said it was not due to a cyber attack.

In February last year, Toyota also had to shut down the same 14 factories in Japan when one of its suppliers, Kojima Industries, which supplies plastic parts and electronic components, said one of its file servers had been infected with a virus that carried an undisclosed threatening message.

That attack raised questions about the cybersecurity of Japan’s supply chain.

What is Toyota’s production and supplier management system?

Toyota essentially invented modern auto assembly with its “kanban” system for notifying suppliers of what parts are needed where and when to minimize inventory.

“Kanban” means signboard in Japanese, and the Toyota engineer and later executive, Taichi Ono, who developed the system drew inspiration from watching an American supermarket chain, Piggly Wiggly, manage its shelf stock on a trip to the U.S. in the 1950s.

Toyota’s system of lean production and just-in-time parts delivery has been adopted across the auto industry and widely studied. It shifted from a system of printed cards that managed supplier workflow to an internet-based “e-kanban” system more than 20 years ago.

Toyota’s kanban system, which relies on simple visual cues to organize workflow, has been adopted for other industries, including software development.

What other problems has Toyota faced since its leadership transition?

Koji Sato took over from Toyota Chairman Akio Toyoda as CEO in April.

In the months since, even as the company looks to overhaul its approach to electric vehicles and related manufacturing challenges with an eye on U.S. EV leader Tesla, it has also reported some embarrassing missteps.

In April, Toyota said affiliate Daihatsu had rigged part of the door in side-collision safety tests for some 88,000 small cars, most of which were sold under the Toyota brand.

In May, Toyota said it had inadvertently exposed customer data on the Internet for more than 2 million Toyota owners because of an error in how it had configured a cloud-based system it uses to track service.