Sao Paulo, Brazil ? The American pilots of an executive jet involved in a deadly high-altitude collision with a Boeing 737 have denied they turned off the transponder that signaled their location, authorities said Thursday.

Pilots Joseph Lepore, of Bay Shore, N.Y., and Jan Paladino, of Westhampton Beach, N.Y., repeatedly told investigators they never turned off the device that transmits a plane’s location and believed that it was working just before the collision, said Denise Niederauer, a spokeswoman for the Mato Grosso do Sul State Public Safety Department.

Brazilian authorities suggested a day earlier that the pilots may have turned off the device.

Authorities did not say why they believed that may have happened, but said a nonfunctioning transponder was a possible cause of the collision with Gol Airlines Flight 1907, which plunged into the Amazon jungle a week ago, killing all 154 aboard in Brazil’s worst air disaster. Gol initially had said there were 155 aboard, but on Thursday changed it to 154, blaming a mistake on the passenger list. The airline said a name had appeared twice on the list.

The Brazilian-made Embraer Legacy 600 executive jet was damaged, but landed safely at an air force base.

The air force said both jets were equipped with a modern traffic collision avoidance system that monitors other planes and sets off an alarm if they get too close, but the system only works if the transponders are working properly.

If the American pilots are found to be responsible for turning off the transponder, which is illegal under Brazilian law, prosecutors said they could be charged with involuntary manslaughter. Authorities said, however, that there was not enough evidence to accuse anybody.

The pilots’ passports were seized Wednesday, but they were not arrested.