TOKYO – U.S. investigators said Wednesday they asked Boeing Co. to provide a full operating history of lithium-ion batteries used in its grounded 787 Dreamliners as Japan's All Nippon Airways revealed it had repeatedly replaced the batteries even before overheating problems surfaced.

National Transportation Safety Board spokesman Peter Knudson said the agency made the request after becoming aware of battery problems at ANA that occurred before two recent incidents involving the planes batteries. Boeing has already collected some of the information, he said.

All 50 of the Boeing 787s in use around the world remain grounded after an ANA flight on Jan. 16 made an emergency landing in Japan when its main battery overheated. About a week before that, a battery caught fire in a 787 parked at Boston's Logan International Airport.