Further testing still has not found the cause of a battery fire aboard a Boeing 787 Dreamliner in Boston earlier this month, the National Transportation Safety Board said on Sunday.

Two weeks ago the US Federal Aviation Administration said both batteries had leaked electrolyte fluid, and there had been smoke damage to parts of the aircraft.

The joint U.S. and Japanese investigation into the Boeing 787’s battery problems has shifted from the battery-maker to the manufacturer of a monitoring system.

Japanese carrier All Nippon Airways was the “launch customer” for the 787, and has been forced to cancel services — 643 domestic flights through Feb. 12, affecting 69,000 passengers, and 195 international flights through Feb. 18, affecting 13,620 passengers.

Photo: Rob Vogelaar Z.A.P.P.