Boeing says it is redesigning electrical panels on the 787 Dreamliner and updating its systems software after a fire broke out on one of its test flights earlier this month.

Boeing issued a statement Wednesday saying it is redesigning the power-distribution panels on the 787 Dreamliner and updating its systems software as a result of the fire aboard one of its test flights earlier this month.

“We have successfully simulated key aspects of the onboard event in our laboratory and are moving forward with developing design fixes,” Scott Fancher, vice president and general manager of the 787 program, said in the statement.

Engineers have determined that the fault began as either a short circuit or an electrical arc in the P100 power-distribution panel, most likely caused by the presence of foreign debris, the company said. It characterized the design changes as minor.

The P100 panel is one of five major power-distribution panels on the 787. It receives power from the left engine and distributes it to an array of systems.

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The fire broke out as the plane was approaching Laredo, Texas, forcing an emergency landing on Nov. 9. It caused smoke in the cabin and some structural damage.

Boeing doesn’t know what the foreign object was, because whatever it was burned up in the fire, spokeswoman Lori Gunter said.

“It was small, it wasn’t as big as a tool,” she said. “A tool would leave evidence.”

The jet is almost three years behind schedule after six delays as Boeing struggled with new materials, parts shortages, redesign work and a greater reliance on suppliers. The plane has been flying since December 2009 in tests toward certification for passenger service, which Boeing had targeted for the first quarter of 2011.

The statement said a revised 787 program schedule is expected to be finalized in the next few weeks. The Federal Aviation Administration must approve the plan before flight tests can resume.

Boeing shares on Wednesday rose $1.81, or 2.9 percent, to close at $65.41 on anticipation that any delay news wouldn’t be as bad as some people had feared.