NEW YORK Some 39 million viewers watched the documentary ***"9/11"*** by French filmmakers Jules and Gedeon Naudet, CBS Television said Monday.

The network, which purchased the rights to broadcast the film in the United States, said 38.98 million people tuned in to the documentary when it aired at 9:00 PM Sunday -- more viewers than any other non-sports program this season, it said.

The figure represents one third of all televisions being watched at that hour, according to Nielsen figures.

Images filmed by Jules Naudet, the only known cameraman on the scene when hijacked airliners struck the World Trade Center the morning of September 11, form the core of the film, narrated by actor Robert de Niro.

Naudet and his brother Gedeon Naudet had since June been making a documentary on the life of a rookie fire fighter assigned to southern Manhattan's Engine 7, Ladder 1 Unit, a stone's throw from the World Trade Center.

Thanks to a firefighter friend, the brothers got unprecedented access to the firehouse. They ate, slept and worked with the 55 firefighters of the unit, getting to know them, and winning their trust while keeping the cameras rolling.

Since June, the filmmakers had seen little action -- long stretches in the firehouse broken by a few call-outs for non-emergencies such as fires in garbage cans.

Jules Naudet was on just such a call-out -- a gas leak -- early on September 11 when the world changed.

Hearing the jet engines, Naudet pointed his digital camera upwards and captured the only known footage of the first airliner smashing into WTC tower number one.

All told, the French brothers captured 180 hours of film from inside and outside the WTC as the tragedy unfolded and some 3,000 people died.

CBS produced a two-hour documentary from the footage. A longer film is in the works.