Board chairman Adm. Hal Gehman said the panel would meet with engineers at Johnson Space Center on Monday before fanning out to other NASA centers. He said the pace of the probe will triple after Monday because members will split into three teams, each taking on different aspects of the complex investigation.
The NASA-appointed board has less than two months to complete the investigation, but Gehman said that deadline may be extended because "the first imperative is to get it right."
Gehman said Sunday that investigators were looking into data from military radar of an object detected speeding away from Columbia on Day 2 of its mission. Gehman said the object — detected by Air Force Space Command radar — could have come from the spacecraft and could be ice, but emphasized that more study is needed.
"These reports are emerging right now," he said. "It's too early to say they mean anything."
CBS News Space Consultant Bill Harwood reports Air Force tracking radar indicates that something appears to be separating from the orbiter about five meters per second — about 11 miles per hour.
Obviously, if something did come off the shuttle with the velocity like that, it implies that perhaps the shuttle was struck by something, with space debris being a possibility, and that could then explain what might have weakened the wing and the thermal system of the shuttle to leave it vulnerable during re-entry.
NASA began a detailed search for evidence that ice may have formed on the shuttle's waste water vent during its mission — a problem that plagued a Discovery mission in 1984.
The vent, which is under the shuttle cabin in front of the left wing, is used to expel into space both urine and surplus water generated from the shuttle's fuel cell power system.
Usually the water shoots into the cold vacuum of space as a spray of crystals, but on at least one shuttle mission, in 1984, the water formed a basketball-sized chunk of ice on the lip of the vent. At the time, NASA engineers were so concerned the ice could damage the shuttle wing during re-entry that they ordered the astronauts to use the shuttle's robot arm to break off the ice ball.
That heavy robot arm, which wasn't necessary for Columbia's 16-day science mission, was left off so more experiments could added, and the waste water vent could not be seen from the cabin by the seven astronauts. NASA spokesman Kyle Herring said it's possible ice could have formed and not been detected, even though heaters were installed on the waste water dump valve after the 1984 mission.
When Columbia fired its rockets to drop out of orbit, it could have sent any accumulated ice slamming into the wing where other data suggests there was severe damage to the thermal protection tiles. The theory is unproven and is only one of a number of scenarios being probed by engineers.
NASA administrator Sean O'Keefe said Sunday that no theory has been excluded.
"Nothing is off the table," he said on CNN. "We're going to let the Columbia accident board guide us in terms of their findings about what caused this accident."
More than 12,000 pieces of debris have been located in Texas and Louisiana, including a 2-foot piece of one wing, an attached chunk of thermal tiles, and a 300-pound cover of a landing gear compartment. Officials were unable to say whether those pieces came from the shuttle's left side, which would make them significant in their investigation.
One object, which appears to be a hatch door with a hydraulic opening and closing mechanism, was found Sunday. O'Keefe said the debris will be transported to Kennedy Space Center starting this week where investigators will attempt to reassemble as much of it as possible.
"There is certainly no way we are going to be able to reconstruct it. The pieces are just absolutely mangled," O'Keefe said. "It's an awful lot of tangled stuff."
The wing segment and landing gear compartment door found in Texas have captured the attention of engineers because they could have been near areas where the shuttle registered a rapid temperature rise during the last minutes of flight Feb. 1.
Mission Control received data from Columbia that showed a sudden rise in temperature in the left landing gear compartment and along the left side of the fuselage. The data also shows increased wind resistance from the left wing, forcing the autopilot to rapidly move control surfaces and fire jets to maintain stability. The craft seemed to be losing the control battle, engineers said, just before all communications with Columbia stopped.
NASA's shuttle missions are on hold now, but O'Keefe said Sunday that the agency is still preparing to resume flights as soon as the cause of Columbia's breakup is determined and any shuttle flaws are fixed. "We've still got folks aboard the international space station," he said.
CBS News Space Consultant William Harwood has covered America's space program full time for more than 15 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.