24/7 Wall St.

There is no hope in sight for Boeing Co. (NYSE: BA) as it tries to get its 787 Dreamliner flagship back in the air. Japanese investigators say that an overcharging of the plane’s lithium-ion battery is not at fault. The U.S. Department of Transportation says it has not found the source of the problem, but will continue to work “round the clock” to locate it.

All the while, deliveries of the Dreamliner are on hold, and Boeing’s shares continue to trade down.

According to Bloomberg:

U.S. Transportation Secretary Ray LaHood and FAA Administrator Michael Huerta gave no indication yesterday that the Dreamliner will return to service soon, as regulators around the world try to figure out what triggered smoke and fire earlier this month on two Japanese airliners, one of which made an emergency landing.

“Our goal is to get this done as quickly as possible, but we must be confident that the problems are corrected before we can move forward,” LaHood said at a meeting of the Aero Club of Washington. The Transportation Department and the Federal Aviation Administration “are working diligently with Boeing” to find a solution, LaHood said.

“We don’t know what caused these incidents yet,” Huerta told reporters at a briefing after LaHood’s remarks.