Columbia's sensors showed a sharp rise in temperature as the spacecraft headed over land from the Pacific, and NASA said it may have found a piece of the wing in California.

Despite locating thousands of pieces of the shuttle in Texas and Louisiana, NASA officials hoped to find clues to the earliest moments of the accident in the far West.

The flight was normal "until we got into the area somewhere over the skies of California, roughly," Michael Kostelnik, a NASA deputy administrator for spaceflight, said today.

Despite the early hour, many people were watching as Columbia swept west to east over California shortly before 6 a.m. PST Saturday ­ about six minutes before it disintegrated over Texas. It was traveling on a line slightly north of California's midsection ­ from near San Francisco, across the Central Valley and the Sierra Nevada mountains.

Amateur astronomer Rick Baldridge photographed and videotaped Columbia as it passed over San Jose, south of San Francisco. He said the video showed flares of light that appeared to be parts breaking off the shuttle.

Another amateur astronomer made a digital time-exposure photograph in San Francisco that showed a snake of purplish light corkscrewing through the shuttle's hot glowing trail, the San Francisco Chronicle reported today. A former astronaut collected the camera from the photographer, who requested anonymity pending NASA's analysis.

"They are going to see if there's anything in the camera that could have caused the blur," said NASA spokeswoman Katherine Watson. "They are going to see if it's real or if it's an artifact."

She said NASA has received 1,300 images of Columbia from eyewitnesses.

Astronomer Anthony Beasley, a program manager at the California Institute of Technology's Owens Valley Radio Observatory, watched from his home in remote Bishop on the east side of the Sierra Nevada as the shuttle soared across the dark sky.

Beasley noted three flashes in the brightness of the streaking shuttle. Within hours he had written a detailed report that noted he was aware shuttles sometimes lost thermal tiles during landing and he immediately thought he might have seen that.

"Possibly saw secondary material in trail immediately after," he wrote of the first flash. "At the time I thought ­ it must have lost a tile...."

After the second flash "there was clearly a new trail formed ... directly behind the orbiter" and what seemed to be "a main piece and a few smaller bits" fell behind and appeared to fall, he wrote.

The third flash appeared the brightest to Beasley.

"Very clear view of object detaching, forming separate trail. Looked like orbiter dropped a flare or something," he wrote.

Beasley said in interviews that he believes his sighting and others could be used to estimate a location where an object fell. But he cautioned that actually finding something could be daunting in the rugged wilderness, where peaks stand thousands of feet high.

"These are some of the most sparsely populated counties in North America," he said. "This thing could be sitting out among two clumps of sagebrush and won't be found for 50 years."

About the same time Beasley was watching, Jay Lawson was videotaping about 160 miles to the northwest in Sparks, Nev. He said the tape showed a bright flash and an object trailing slightly behind the shuttle.