TOKYO — The joint U.S. and Japanese investigation into the Boeing 787’s battery problems has shifted from the battery-maker to the manufacturer of a monitoring system.

Japan 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 problems.

Ministry officials said they will inspect Kanto Aircraft Instrument today as part of the ongoing investigation. It makes a system that monitors voltage, charging and temperature of the lithium-ion batteries.

All 50 of the Boeing 787s in use around the world are grounded after one of the jets operated by All Nippon Airways made an emergency landing in Japan earlier this month when its main battery overheated. Earlier in January, a battery in a Japan Airlines 787 caught fire while parked at Boston’s Logan International Airport.