By Antoni Slodkowski TAKAMATSU, Japan, Jan 18 (Reuters) - A team of experts from U.S. aviation authorities and Boeing Co arrived in western Japan on Friday to inspect a passenger jet operated by All Nippon Airways Co that made an emergency landing earlier this week. The incident prompted regulators in the United States and around the world to ground the Boeing 787 Dreamliner jets. Battery-related problems are being investigated after warning lights indicated a battery problem on the ANA flight on Wednesday. All passengers and crew were safely evacuated from the plane. The lightweight, mainly carbon-composite aircraft has been plagued by mishaps, raising concerns over its use of lithium-ion batteries. The five representatives from the U.S. National Transportation Safety Board (NTSB), Federal Aviation Administration (FAA) and Boeing are to assist Japanese authorities in the investigation of the ANA 787 Dreamliner, which remains parked on the side of the Takamatsu airport. "We are joining the JTSB (Japan Transport Safety Board) team today. We are here to support the JTSB," Lorenda Ward from the NTSB told reporters at the Takamatsu airport. GS Yuasa Corp, the Japanese company that makes the batteries for the Dreamliner, also said it had sent three engineers to Takamatsu in western Japan to help the investigation. Regulators in Japan said it was unclear when the Dreamliner could be back in the air. Japan is the biggest market so far for the Dreamliner, with ANA and local rival Japan Airlines Co Ltd operating 24 of the 50 Dreamliners delivered to date. Keeping the 787s on the ground could cost ANA alone more than $1.1 million a day, Mizuho Securities calculated, noting the Dreamliner was key to the airline's growth strategy. JAL said on Thursday it had cancelled eight Dreamliner flights between Tokyo and San Diego until Jan. 25, affecting some 1,290 passengers, and would switch aircraft for another 70 flights scheduled to fly the 787. The JTSB said the battery on the ANA flight that made the emergency landing was blackened and carbonised, the Kyodo news agency reported on Thursday. The use of new battery technology is among the cost-saving features of the 787, which Boeing says burns 20 percent less fuel than rival jetliners using older technology. The 787, with a list price $207 million, represents a leap in aircraft design, but the project has been plagued by cost overruns and years of delays.