US and Japanese authorities have begun a joint investigation into GS Yuasa, the Japanese battery maker for Boeing's troubled 787 Dreamliner aircraft.
It comes after an All Nippon Airways (ANA) 787 had to make an emergency landing due to a battery malfunction.
However, another US regulator said on Sunday the battery did not overcharge in a separate incident involving a Japan Airlines (JAL)-operated 787.
Regulators have grounded all Dreamliners currently in operation.
ANA has announced 335 Dreamliner flight cancellations including up until next Sunday. This is set to affect 48,000 passengers, including almost 4,000 international passengers.
Yasuo Ishii, a Japanese transport ministry safety official, said: "Engineers from the [US Federal Aviation Administration], Boeing and our aviation bureau started a probe this morning that is mainly focusing on GS Yuasa's production line.
"They are checking on whether there have been any issues in the production process. We still don't know what caused the battery problem, and so we are looking into all possibilities."
Japanese battery maker GS Yuasa has seen its shares fall 11% since 7 January when an electrical fire broke out on a JAL 787 at Logan International Airport in Boston, although they rebounded 1% on Monday as it became apparent the fault may not have been a pure battery problem.
Investigating that incident, the US National Transportation Safety Board (NTSB) said the battery did not overcharge.
"Examination of the flight recorder data from the JAL B-787 airplane indicates that the [auxiliary power unit] battery did not exceed its designed voltage of 32 volts," the NTSB said in a statement on Sunday.
It said it would now widen its probe to look at the battery charger and the auxiliary power unit.
GS Yuasa also produces batteries for motorbikes, industrial equipment and power supply devices.
Last week, the Federal Aviation Administration (FAA) said both batteries had leaked electrolyte fluid, and there had been smoke damage to parts of the aircraft.
The NTSB said a group of experts would meet in Arizona this week, where the battery charger is manufactured by Securaplane Technologies, to test and examine the part.
The battery charger maker, a unit of Britain's Meggitt, said it would fully support the US investigation. United Technologies, which builds the aircraft's auxiliary power unit, said it would also cooperate.
On Friday, Boeing said it would put deliveries of the 787 on hold until the FAA approved its plan to ensure the safety of the batteries.
It said it would, however, continue building the light-weight fuel-efficient plane.
Japan is the biggest buyer of the aircraft, with ANA and JAL operating 24 of the 50 Dreamliners currently in operation.
Boeing has orders for more than 800 Dreamliners.