The joint US and Japanese investigation into the Boeing 787's battery problems has moved from the battery-maker to the manufacturer of a monitoring system. Transport ministry official Shigeru Takano said today the probe into battery-maker GS Yuasa was over for now as no evidence was found it was the source of the problem.

Ministry officials said they are inspecting Kanto Aircraft Instrument Co. later in the day as part of the ongoing investigation.

It makes a system that monitors voltage, charging and temperature of the lithium-ion batteries.

All Boeing 787s are grounded after one of the jets made an emergency landing in Japan earlier this month when its main battery overheated.

Earlier a battery in another 787 caught fire while parked at Boston's Logan International Airport.