Bronson, Texas-AP -- There's no sign yet in Texas of a secret communications device NASA is looking for among "Columbia's" wreckage.
NASA says the box allows communications between the shuttle and ground controllers to be encrypted.
Officials say if somebody else finds the device, they could study the technology and possibly send "bogus" signals to future shuttle missions.
National Guardsmen spent yesterday combing an area around Bronson, Texas -- near the Louisiana border. But they came up empty.
One resident says searchers had been in the area for at least a couple days.