Airline safety inspectors have found no faults with the battery used on Boeing’s 787 Dreamliner, Japan’s transport ministry has announced.

Dreamliner’s battery was initially considered the likely source of problems on 787s owned by two Japanese airlines.

The world’s entire fleet of 50 787s has been grounded while inspections are carried out.

Attention has now shifted to the electrical system that monitors battery voltage, charging and temperature.

Transport ministry official Shigeru Takano said “we have found no major quality or technical problem” with the lithium-ion batteries. Shares in GS Yuasa, which makes the batteries, jumped 5% on the news.

“We are looking into affiliated parts makers,” he said.

“We are looking into possibilities.”

Airline safety inspectors have found no faults with the battery used on Boeing’s 787 Dreamliner

The safety investigation started after one of the 787s operated by All Nippon Airways made an emergency landing in Japan when its main battery overheated. Earlier, a battery in a Japan Airlines 787 caught fire while parked at Boston’s Logan International Airport.

Two weeks ago the US Federal Aviation Administration said both batteries had leaked electrolyte fluid, and there had been smoke damage to parts of the aircraft.

The FAA said airlines must demonstrate battery safety before flights could resume, a statement that effectively meant airlines had to ground their 787s.

Boeing, which competes against Europe’s Airbus, has halted 787 deliveries. Boeing has orders for more than 800 Dreamliners.

The 787 is the first airliner made mostly from lightweight composite materials that boost fuel efficiency. It also relies on electronic systems rather than hydraulic or mechanical systems to a greater degree than any other airliner.