The American investigators — one each from the Federal Aviation Administration and the National Transportation Safety Board and two from Boeing Co. — inspected the ANA jet on the tarmac at Takamatsu airport in western Japan.
An initial inspection by Japanese officials of the 787 found that a flammable battery fluid known as electrolyte had leaked from the plane's main lithium-ion battery beneath the cockpit. It also found burn marks around the battery.
Aviation authorities in Japan have directed ANA, which owns 17 of the planes, and Japan Airlines, with seven, not to fly the jets until questions over their safety have been resolved.
The 787, known as the Dreamliner, is Boeing's newest jet, and the company is counting heavily on its success. Since its launch after delays of more than three years, the plane has been plagued by a series of problems.
The FAA has required U.S. carriers to stop flying 787s until the batteries are demonstrated to be safe. United Airlines has six of the jets and is the only U.S. carrier flying the model.
Aviation authorities in other countries usually follow the lead of the country where the manufacturer is based.
Associated Press writer Mari Yamaguchi contributed.