Debris crews combed an area along the Texas-Louisiana border for the wreckage of a secret device that allowed the encryption of communications between NASA and the shuttle Columbia.

NASA spokesman John Ira Petty said Friday that finding the box was a high priority because officials feared its technology could be used "to send bogus signals" to the other shuttles during future flights.

"We are searching for all debris. Certainly we would like to recover this one," Petty said.

Officials did not explain why they focused their search for the device on an area around Bronson, which is on the southern edge of the main debris field in East Texas.

David Williams, an on-scene search coordinator with the Environmental Protection Agency, said searchers spent Thursday in an area near Bronson. "They said they came out of there with very little," he said.

Williams' search party found a black box with a serial number about five miles east of Bronson, "but it didn't appear to be the black box NASA was looking for," he said.

Bronson residents said about 80 National Guard members arrived in camouflage-hued trucks and were accompanied by state troopers as they searched the woods Thursday.

"They were everywhere," said Beth Walker. They didn't say what they were looking for but told her to report downed tree limbs or uprooted ground, she said.

So far, searchers have found and cataloged the locations of more than 12,000 pieces of debris across Texas and Louisiana. The debris will be taken to Barksdale Air Force Base, La., then to Kennedy Space Center in Florida for reconstruction, officials said.