A cold rain created the most adverse weather the teams have faced since the breakup of the shuttle Saturday that killed seven astronauts.
"I've never seen a more dedicated group in all my years in law enforcement," said Sabine County Sheriff Tommy Maddox. "I don't think there is anything that could prevent them from accomplishing what they want."
About 200 Texas National Guard troops were expected to join the hundreds searching the area about 180 miles southeast of Dallas.
More than 12,000 pieces of debris have been recovered in east Texas and western Louisiana, according to federal officials. Remains of the astronauts were flown to Dover Air Force Base, Del., for identification Wednesday.
Although pieces of the shuttle's nose cone, control panel, and superstructure have been recovered, none of the hardware NASA officials believe is critical to the investigation has been found so far.
"We do not have any red-tag items," said Ron Dittemore, shuttle program manager, during a NASA briefing late Wednesday.
Dittemore said they would like to find parts of the left wing, data recorders and pieces of the tiles and insulation.
Although most of the debris has been found around Hemphill and Nacogdoches in east Texas, the current search area extends from California to western Louisiana.
Columbia was headed for a landing in Florida when it tore apart over Texas at more than 200,000 feet, traveling 18 times of the speed of sound.
Police officers and firefighters from California, Florida, New York City, and British Columbia and an Israeli search and rescue team have joined the massive recovery. Col. Ilan Ramon of Israel was one of the astronauts killed in the mishap.
Law enforcement is also dealing with those who want to take advantage of the shuttle tragedy.
Texas Attorney General Greg Abbott issued a warning Thursday for consumers to be on the lookout for telephone and e-mail scams asking for donations of money to aid the families of the Columbia astronauts.
"With the nation still grieving over the loss of these American heroes in the skies above Texas, we now have information that professional scam artists are using this tragedy to prey on the good will of our people," he said.
Abbott promised to crackdown on any illicit solicitations by phone or on the Internet.
A fund created to assist the families of the 1986 Challenger disaster is being reconstituted to provide a legitimate fund for contributions, he said.
Federal prosecutors also warned anyone who picked up debris to turn it into authorities by 5 p.m. Friday or face prosecution.
A man and woman were arrested Wednesday in east Texas on charges of stealing debris from the shuttle.
Merrie Savage Hipp, 43, of Henderson and Bradley Justin Gaudet, 23, of Nacogdoches both pleaded innocent later before a U.S. magistrate. They were released on their own recognizance until their trials scheduled April 8.
U.S. Attorney Michael Shelby of Houston said amnesty was being offered to encourage anyone holding shuttle debris to immediately turn it over to authorities.
"No one knows which piece will reveal the cause of this accident," he said. "Every piece is potentially crucial to the investigation. Do not make a tragedy worse by your own selfishness."
A conviction for the theft of government property can bring up to 10 years in prison and a $250,000 fine.
(Reported by Phil Magers in Dallas)