US aerospace giant Boeing blamed a fire aboard a test 787 Dreamliner plane on faulty power panels as the already-delayed program reeled from its latest setback.
"We have determined that a failure in the P100 panel led to a fire involving an insulation blanket," the plane-builder said in a statement.
Found under passenger seats close to the wings, the P100 panel is one of the aircraft's numerous power panels. It obtains power from the left engine and distributes it to a range of systems.
Boeing said damage to the panel was "significant," but noted that initial inspections did not show extensive damage to the surrounding structure or other systems.
"The backup systems engaged during the incident and the crew retained positive control of the airplane at all times and had the information it needed to perform a safe landing," it added.
Though molten metal was found near the panel, Boeing said it had little significance to the investigation.
The firm did not indicate when test flights would resume.
On Wednesday, Boeing halted tests for the new 787 Dreamliner, whose program is already running about three years behind schedule.
Boeing announced the decision after the fire on Tuesday forced an emergency landing in Laredo, Texas. Smoke filled the ZA002, one of the company's six test 787s, but it was able to land safely with 42 passengers.
It said the fire was the most serious incident since test flights began in December 2009.
The 787 Dreamliner, launched in April 2004, has suffered a series of setbacks, many of them from challenges in the international production of parts for the mid-size plane.
Boeing says the high-tech 787, made essentially from composite materials, will deliver a 20 percent reduction in fuel consumption compared with planes of similar size flying today.
The first 787 was initially promised to Japanese launch customer All Nippon Airways in the first half of 2008. Delivery has now been pushed back to around February 2011.
Explore further: Key decisions on drones likely from Congress