KYOTO, JAPAN -- U.S. and Japanese aviation safety officials are investigating the company which makes the batteries for Boeing's troubled Dreamliner aircraft, the global fleet of which has been grounded following a series of safety scares.

According to Reuters news agency a spokesman for GS Yuasa Corp. said investigators from the Federal Aviation Administration and Japan's Civil Aviation Bureau (CAB) were at the company's offices in Kyoto, where it makes airplane batteries.

The spokesman said the company was "fully cooperating" with FAA and CAB officials.

Boeing halted deliveries of its lightweight 787 - dubbed 'the plastic plane', thanks to its near-50 percent carbon composite makeup - after a problem with a lithium-ion battery forced an All Nippon Airways 787 to make an emergency landing last week.

The incident was the latest in a series of incidents that have raised concerns about the safety of the technologically advanced airliner.

Reuters reported that U.S. officials were looking at the battery's charger and the jet's auxiliary power unit.