French investigators who found trace levels of the explosive material TNT on debris of an EgyptAir plane that crashed in May were prevented from further examining it, Le Figaro reported on Friday, a charge Egyptian officials denied.

The origin of the traces remains unclear and Egyptian judicial authorities did not allow French investigators to examine the debris in detail, Le Figaro said, citing a source close to the investigation.

EgyptAir flight MS804, an Airbus A320, plunged into the eastern Mediterranean en route from Paris to Cairo on May 19. All 66 people on board were killed, including 15 French passengers. The cause of the crash remains unknown.

Egypt wishes to write a joint report with France to validate the presence of TNT on the debris. France has refused to do this because the investigators were not able to carry out an adequate inspection to determine how the traces could have got there, Le Figaro said.

Responding to Le Figaro's report, sources on the Egyptian-led investigation committee denied the French team's work had been obstructed.

"None of the investigators were prevented from participating in investigations, but rather the work is being done jointly according to the conduct of the investigative process," one of the committee sources said.

A spokesman for the French national police has declined to comment on Le Figaro's report.

Audio from the flight recorder of the crashed aircraft mentions a fire on board the plane in its final moments, the investigation committee said in July.

Earlier analysis of the plane's flight data recorder showed there had been smoke in the lavatory and avionics bay, while recovered wreckage from the jet's front section showed signs of high-temperature damage and soot.

A committee source said the cause of the fire was still being investigated and it was too early to determine a cause.