Any debris spotted in New Mexico could be among the first pieces of the shuttle to come apart. No debris has yet been confirmed west of Texas, but NASA says Columbia's troubles Feb. 1 started well off the California coast, and they have photos and eyewitness reports from California through New Mexico.
The state's governor, Bill Richardson, says NASA believes a piece of shuttle wing might have fallen in the mountains there.
The Sandia Mountains east of Albuquerque were targeted after people reported hearing a whooshing sound about the time the shuttle passed overhead, said Peter Olson, a spokesman for the state Department of Public Safety. He said there also was radar evidence, but he didn't know what.
"One of the things they are looking for is reinforced carbon-carbon, which is part of the leading edge of the wing, a protective part on the front side of the wing," he said. "They're hopeful they can find something because it would be an important part of the puzzle."
Part of the shuttle's left wing was found over a week ago in eastern Texas, where much of the debris has turned up, and authorities were continuing the search there Saturday.
In New Mexico, about 140 searchers headed into a rugged two-square-mile area of Embudito Canyon on the west side of the Sandia Mountains. The canyon is covered by juniper and pines and ranges in elevation from about 6,500 to 8,500 feet, narrowing and becoming steeper at higher terrain.
Authorities closed the area to hikers during the search.
Meanwhile, investigators said Saturday they've learned that two more of the space shuttle's control jets kept firing in the final minutes as "Columbia" tried to maintain control, meaning at least four jets were trying unsuccessfully to keep the shuttle on course.
The information came from the final 32 seconds of ragged data sent by the shuttle.
Two weeks after Columbia was destroyed, a hole in the spacecraft's aluminum skin that left it vulnerable to super-hot gases has become a suspect in the space shuttle's disintegration.
But as the Columbia investigation board continues visiting NASA centers to gather information, its members, as well as agency officials, stress the breach is one of many possible causes of the accident they are studying.
While the board has acknowledged superheated air probably seeped through a breach in Columbia's left wing and possibly its wheel compartment during the craft's fiery re-entry, investigation board chairman Adm. Harold Gehman Jr. said all possible causes, including sabotage, are still being reviewed.
"Everything is on the table. We release information as we get it. But that doesn't mean there's any special significance to it," he said.
On Saturday, the board toured Lockheed Martin Corp.'s facility in Louisiana, where shuttle external tanks are built. Gehman said the purpose was to get an understanding of the tank's production process and a smaller team likely would return next week to begin collecting data.
Earlier Saturday, as members left Marshall Space Flight Center in Alabama, Gehman confirmed that former Air Force Secretary Sheila E. Widnall had been appointed to the board. He said the Massachusetts Institute of Technology professor, who studies high-altitude flight, has the experience to help figure out Columbia broke apart.
The addition of Widnall will bump the board to 10 members, many of the connected to the Air Force.
In a telephone interview from her home Saturday, Widnall said it appeared that the high heat of re-entry, rather than aerodynamic stress on the shuttle, was at the heart of the shuttle's Feb. 1 breakup.
"That was my gut reaction as I sat there all day that day watching the coverage," she said.
The board has also traveled to Kennedy Space Center in Florida.
Flight director Leroy Cain, who was on duty Feb. 1 when the shuttle broke apart, also didn't want to place too much emphasis on the breach at this stage in the investigation.
"It's a possibility, along with the whole range of things that are possibilities. But there are many, many other possibilities," Cain said Friday.
Analysis of what could have caused a hole in the shuttle continues. One possibility raised from the very start of the investigation, is that Columbia was damaged by a hard piece of foam insulation that fell off the external fuel tank during liftoff.
George J. Gleghorn, a retired TRW Inc. engineer and former member of the NASA Aerospace Safety Advisory Panel, said he believes the breach probably happened during liftoff.
"I would be surprised if something happened that caused a breach of the skin without being noticed unless it was that incident that happened during the ascent phase," Gleghorn said.
Cain acknowledged Friday he immediately thought of the foam debris right after he was first told of sensors breaking down in the spacecraft's left wing minutes before it came apart over Texas, killing its crew of seven astronauts.
"That gave me pause," Cain said. But he also said when he learned about the sensor readings, he did not imagine it would spell the end for the shuttle and its crew: "I did not think that we would lose it."
Investigators believe the breach allowed a stream of superheated gases to penetrate the shuttle's left wing, starting a cascade of failures.
One by one, sensors in Columbia's left wing recorded unusual readings as the shuttle approached the California coast. The precise meaning of those readings was not immediately clear to Mission Control, Cain said.
The wings have only a few sensors, not enough to indicate if the landing gear hatch had come open or had been breached to allow the superheated gases, called plasma, to penetrate the wing, he added.
Most ominous of the readings was a spike in temperature in the compartment containing Columbia's left landing gear that suggests gases 2,000 degrees or hotter had infiltrated the shuttle.
To do so, they would have had to bypass the layer of tiles and other insulating material designed to protect the spacecraft from the searing heat of re-entry. The investigation board has said missing tile would not have allowed heat to simply radiate into the interior of the wing and cause the rise in temperature.
Cain said Friday he doesn't believe his flight team could have done anything different to prevent the disaster.
Gehman said he will add one or two authorities in high-altitude aerodynamics and thermal engineering to the nine-member board to bring more expertise to the investigation. The board will also conduct some key tests independently of NASA, but not double-check everything the agency does, he said.
The board has been criticized by members of Congress and others as not being sufficiently independent of NASA.