NACOGDOCHES, Texas (AP) -- Under rain clouds that threatened to hamper their search, authorities returned to the forests of East Texas on Monday to hunt for more debris from the space shuttle Columbia and remains of its seven astronauts.
Hundreds of investigators with expertise in airline accidents, engineering and forensics converged on Texas and Louisiana to join in the painstaking job of retrieving pieces of wreckage from a huge swath of forested country bigger than the state of West Virginia.
Teams of global positioning satellite technicians were back in the field at daybreak to continue logging the location of debris for investigators, said James Kroll, director of the Emergency Geospatial Mapping Center at Stephen F. Austin State University in Nacogdoches.
``We're still out there. We've got 15 teams mapping stuff all over, if they ever decide to come pick it up,'' Kroll said.
Overwhelmed local authorities scrambled to locate and guard objects in the sprawling debris field, as NASA established command posts in Lufkin and at Barksdale Air Force Base in Louisiana to oversee recovery and examination of the wreckage.
Among those standing guard was school Principal Jay Tullos, waiting for experts to collect the 25 pieces of debris that had fallen on the grounds of a school in Douglass. Classes were canceled Monday.
``They said they'd be here first thing in the morning. We're waiting on a call,'' Tullos said.
About 300 people from 30 agencies - including the FBI, Federal Emergency Management Agency, National Transportation Safety Board and the Texas Department of Public Safety - were being assigned to collect thousands of pieces as small as pebbles and as big as pickup trucks.
Once in hand, the wreckage will be trucked to Barksdale, where engineers from shuttle contractor United Space Alliance will sort through it in search of clues to what caused Columbia to break apart over Texas on Saturday morning just minutes before its scheduled landing in Florida.
Their goal is to reconstruct what is left of Columbia and establish a sequence of how each part peeled off during its high-speed re-entry into the atmosphere.
The salvage operation covers an area that stretches from the rolling hills of East Texas to a suburb of New Orleans, where authorities found what could be insulation from Columbia.
Louisiana state police said they had taken custody of at least 20 possible shuttle pieces in 10 parishes as of Monday morning.
However, the search for wreckage has focused on Texas, where Gov. Rick Perry said 33 counties _ a 28,000-square-mile area from north of Dallas all the way to the Gulf Coast _ had reported debris. That amounts to about 10 percent of Texas' land area, or more than all of West Virginia.
The heart of the operation is East Texas, a region of thick forests of pines and oaks, expansive farm land and cow pastures. It holds four national forests, covering almost 700,000 acres, and two reservoirs that together span about 300,000 acres. The thick woods also are home to wild hogs and bobcats.
While the region is a magnet for hunters, boaters and anglers, its challenging terrain makes the job facing Columbia recovery teams that much more difficult.
``This is forest _ dense forest,'' said Kroll. ``There is no way to describe how many pieces there are and how spread over the landscape they are.
``Ten years from now, folks are going to be walking around the woods and finding stuff.''
In Nacogdoches County alone, authorities have logged more than 1,200 confirmed debris sites. State troopers and local authorities didn't have enough personnel to protect every piece, but they manned 130 spots _ alongside two-lane highways, restaurants and ranches _ to guard debris against scavengers.
They said NASA had provided a list of priorities: anything that could contain data or resembles computer circuitry, or potentially radioactive materials.