GE has so far found no further evidence of improper installation of low-pressure turbine stage-one nozzles in GEnx engines following its issuance last week of a service bulletin that called for a fleet-wide borescope inspection.

The company issued the bulletin last week after a preliminary examination by Chinese authorities and investigators from the U.S. National Transportation Safety Board uncovered evidence of damage to the “back end” of a GEnx-2B engine on an AirBridgeCargo 747-8 that lost power during a takeoff roll in Shanghai, China, on September 11.

“Initial findings of the damaged engine LPT indicate that an LPT stage-one nozzle may have been improperly assembled and became dislodged, causing damage downstream,” an NTSB spokesperson told AIN on Tuesday. “Efforts are continuing to determine the reason for these observations.”

The failure appears unrelated to a pair of incidents involving a fracture and a crack in a specific area of the fan midshaft in GEnx-1B engines installed on Boeing 787s. The first, involving an Air India Boeing 787 performing ground tests on July 28 in Charleston, S.C., resulted in a contained failure that caused a grass fire next to one of Charleston International Airport’s runways. On August 31, mechanics found cracking in the same area of the fan midshaft in a GEnx-1B on another 787 that hadn’t yet flown.

A GE spokesman said as of Tuesday nearly 50 of the 122 GEnx engines in service had undergone inspection. An inspection takes about an hour to complete and doesn’t require special equipment for the operators, said GE. The service bulletin does not call for repeated inspections.