Contour's solid-fuel rocket motor was placed too far inside its body, the NASA panel reportedly found, and hot gases probably caused the probe to break apart two seconds before the end of a planned 50-second engine burn.
Contour was designed and built for NASA by the Johns Hopkins University's Applied Physics Laboratory near Laurel.
"It's not a finished report," said APL spokesman Michael Buckley. "We'll comment on it when NASA releases the report."
NASA spokesman Don Savage declined to comment on the panel's conclusions. He said the inquiry by the Contour Mishap Investigation Board is continuing. Its report has been delayed, probably until March.
"They're doing a reanalysis on a lot of the work they had done, which is why it is taking longer than originally anticipated," he said. "They're looking at a number of factors."
Theron told the AP that the inquiry could not rule out other possible causes for the mishap, including a collision with space debris.
The lead investigator was traveling yesterday and unavailable for comment, Savage said.
APL controllers lost contact with Contour on Aug. 15, just 48 seconds after its solid-fuel rocket motor fired to boost it out of Earth orbit for its first comet rendezvous.
Where Contour should have been, astronomers instead spotted as many as three bright objects moving away from Earth.
Repeated attempts by APL controllers to contact the spacecraft - most recently in December - were met by silence.
The accident abruptly ended a planned four-year mission. Contour was to have flown by Comet Encke this year, Schwassmann-Wachmann 3 in 2006 and perhaps a third comet in 2008, returning valuable data about the comets' makeup and origins.
Buckley said the placement of Contour's rocket - partly embedded in the body of the spacecraft - was one that APL adapted from the European Space Agency's successful Giotto mission to Halley's Comet. Giotto was launched in July 1985. Its solid-fuel booster later fired as planned, accelerating the spacecraft toward its 1986 Halley's fly-by.
The mission provided scientists with their first close-up image of a comet's nucleus. Giotto flew past a second comet in 1992 and zipped past the earth again in 1999.
Buckley said Contour, like Giotto, needed a solid-fuel booster to get itself out of Earth orbit and head toward its comet encounters.
The design APL chose had two advantages, he said. It offered long-term stability for a spacecraft that had to spin to remain stable for years between comets. It also was compact, allowing Contour to fit inside its Delta 2 rocket.