A spokesman for GS Yuasa Corp, said investigators from the U.S. Federal Aviation Administration (FAA) and Japan's Civil Aviation Bureau (CAB) were in the east block of the company's compound at Kyoto, where it makes airplane batteries.
He said the company was fully cooperating with the investigation, and its engineers were working with the officials.
Authorities around the world last week grounded the new lightweight aircraft, and Boeing halted deliveries after a problem with a lithium-ion battery prompted an All Nippon Airways 787 into the emergency landing at Takamatsu airport during a domestic flight. Earlier this month, a similar battery caught fire in a Japan Airlines' 787 parked at Boston Logan International Airport.
U.S. safety investigators on Sunday ruled out excess voltage as the cause of the Boston battery fire on January 7, and said they were expanding their probe to look at the battery's charger and the jet's auxiliary power unit.
"Results have shown the battery was abnormal in both the Boston and Takamatsu (incidents). They were the most damaged,"
Shigeru Takano, a senior safety official at the CAB, told reporters. Ahead of the on-site visit to GS Yuasa, Takano said: "We will look into if the work that took place, from design to manufacturing, was appropriate."
Shares in GS Yuasa, valued at close to $1.5 billion, rose 1 percent on Monday, having dropped nearly 10 percent since the Boston fire. The benchmark Nikkei was down 1.5 percent.
The company, which employs nearly 12,300 staff, expects revenue of 288 billion yen in the year to end-March - with only around 1 percent of that coming from its aircraft battery business. The company's batteries are used primarily in motorbikes, industrial equipment and power supply devices.
GS Yuasa, in which automaker Toyota Motor Corp has a 2.7 percent stake, reported an operating profit of around $160 million in the year to last March.
The battery is one part of the 787's complex electrical system, built by French company Thales SA.
MORE FLIGHTS CANCELLED
The grounding of the Dreamliner, an advanced carbon-composite plane with a list price of $207 million, has forced ANA to cancel 141 flights between Wednesday and Sunday, affecting more than 18,000 passengers, the carrier said on Monday. Those cancellations added to the 72 flights scheduled for January 19-22 that ANA called off last week.
JAL also cancelled flights on its Tokyo-San Diego route for January 27-28.
Japan is the biggest market to date for the Dreamliner, with JAL and ANA flying 24 of the 50 passenger jets that Boeing has delivered.
Copyright: Thomson Reuters 2013