By ANN Correspondents Pete Combs and Rob Milford

A piece of wing. A charred helmet. A shuttle mission patch.

These are among the thousands of pieces of debris from the doomed shuttle Columbia that rained down on East Texas Saturday.

Recovery workers, still stunned by the scope and proximity of the disaster, continue to search the backroads and piney-woods of East Texas, looking for enough debris to perhaps determine why Columbia fell out of the sky upon re-entry.

A Charred Electronics Component.
A Piece Of Pipe.
A Homecoming That Never Was...

One recovery worker described it as "trying to find a million needles in a haystack that's five thousand square miles wide." The firefighters, rescue workers and the increasing number of National Guard troops are stone-somber as they go about their grim task, first marking off areas where shuttle debris litters the landscape, then waiting for someone with FEMA or NASA to come by, catalog and photograph the wreckage and, eventually, haul it off. Debris is being taken to Barksdale AFB (LA), where it's being carefully inventoried and investigated. Meanwhile, in Houston, hundreds of mourners gathered at the Clear Lake Baptist Church, near the Johnson Space Center, for an evening memorial service. A welcoming ceremony (poster below) for the astronauts, scheduled for Houston Sunday, wasn't even cancelled. It simply didn't take place.

"No Stone Unturned"

NASA Administrator Sean O'Keefe promised Sunday to leave "no stone unturned" in the search for a cause to this second shuttle tragedy.

"We're leaving nothing to chance. We're looking at every piece of evidence, we're securing all the debris and assuring we look at every possible angle of what could have caused this horrible accident," he said on CBS' Face The Nation broadcast.

F-15 and F-16 warplanes are cruising over the huge debris field at loiter speeds of approximately 250 KTS, helping spot debris on the ground. NASA astronauts from the Johnson Space Center in Houston arrived in Nacogdoches at around 1:00 PM CST Saturday to lead the investigation. Troops and helicopters have been sent from Carswell JRB in Fort Worth to help comb the area. The investigation, NASA said, could take months.

Human Remains Among The Debris

Searchers have found human remains along a 60-mile swath of the debris field, from Nacogdoches, through San Augustine to Hemphill. Among the remains found so far, a torso, a heart, a skull and fingers, one of which was wearing a ring. A make-shift morgue has been set up at an elementary school in Hemphill, where the remains are being gathered and turned over to agents from the FBI.

The Coast Guard will reportedly send a boat with sophisticated underwater scanning gear and divers to a large revervoir near Hemphill. Witnesses say a huge piece of the shuttle -- as big as a compact car -- fell into that lake after Columbia disintegrated in flight Saturday. Search crews speculated it could be part of the crew cabin or part of the Shuttle Habitat, a bus-sized environmental enclosure housed in the cargo bay, used as headquarters for the many different science missions conducted during STS-107.

"We will have divers in the water if necessary," said Billy Smith, the local emergency manager.

A Parallel Search: Why?

It's early in the investigation. NASA Chief Flight Controller Ron Dittemore said Saturday the space agency would be very quiet for the next few days, pausing to mourn and reflect on the loss of the Columbia and its crew. Then would begin the process of assessing what happened and making sure it never, never happens again.

Already, attention is focused on the space plane's left wing. It was there a piece of styrofoam insulation smacked into the shuttle just over a minute after lift-off January 16th. On Friday, NASA officials ruled the impact was of no significance to the safety of the shuttle, allowing plans for a normal return to continue uninterrupted. But in the moments just before Columbia broke up, 200,000 feet above East Texas, as temperatures on the heat shield tiles rose above 3000 degrees Farenheit, heat sensors on the left wing began to fail. The failure quickly spread inboard as more temperature sensors failed and tire pressure sensors in the shuttle's left landing gear went offline.

"As we look at that now in hindsight, we can't discount that there might be a connection," said Dittemore.

Heat Tiles Litter The Landscape

Back in Texas, the debris field looks, at first glance, like the widely-strewn wreckage from an airplane crash. But on closer inspection, you see each part is at least partially charred by intense heat. Protective tiles litter the landscape, having fluttered down like snow after the shuttle's break-up. Some of them are barely worn from the excessive heat of the uncontrolled re-entry. Others are worn to barely recognizable nubs.

Residents here have all heard the warnings -- don't touch the debris. Already, more than three dozen people have gone to area hospitals after coming in contact with bits of wreckage. No serious injuries have been reported.

The warm, clear East Texas sky is often punctuated with the sound of low-flying jets and military helicopters buzzing overhead.

The search for debris could take weeks... months... years.

FMI: http://www.nasa.gov, http://spaceflight.nasa.gov