With NASA issuing renewed pleas for residents of Arizona, California and New Mexico to look for possible pieces of the space shuttle Columbia, the sheriff's department here has locked away a small piece of blackened foam in its evidence room.

The foam, about nine inches square, is just one of the many pieces of mysterious debris that Californians moved to sequester as officials suggested that the West could provide a key to what went wrong on the shuttle.

''Anything that came off the vehicle in California, that's like gold,'' said Kyle J. Herring, a NASA spokesman in Houston. ''Now you're talking about something that came off before any of the telemetry started to show them something was wrong.''

The foam turned up in a backyard in a rural area of nearby Woodside, a place best known as home to wealthy Silicon Valley executives. It was double wrapped in plastic and held for a team of inspectors from NASA and the Environmental Protection Agency, who were visiting sites today in Arizona and California.

''They said their main interest in the foam was in tracking the trajectory of the shuttle,'' said Bronwyn Hogan, a spokeswoman for the San Mateo County Sheriff's Department.

The piece of foam was among scores of leads that NASA teams were exploring as the investigation into the shuttle disaster got under way in the states west of the primary debris fields in Louisiana and Texas. The shuttle sliced over California's elbowing midsection several minutes before reaching Texas, passing near San Francisco and traversing the Sierra Nevada.

Officials with NASA said today that they were taking all witness accounts from Western states seriously as clues to what went wrong with the spacecraft -- and where and when it started to go wrong.

Ron D. Dittemore, the shuttle program manager, said at a news briefing in Houston that if debris were found in the Western states ''that would be very, very significant.''

Reports in California of possible shuttle pieces ranged from a metal pipe washed up on a beach in Santa Cruz, about 75 miles south of San Francisco, to a charred metallic object found in a driveway in Joshua Tree, a desert town about 125 miles east of Los Angeles. In Arizona, more than 100 reports have been documented by the Arizona Department of Public Safety, including an item found in a swimming pool and one under a parked truck.

NASA officials were following up on other leads, including a report from just north of the Golden Gate Bridge of bright flashes in the sky when the shuttle passed overhead, said Laura L. Gentile, a spokeswoman for the E.P.A. in San Francisco.

There was also interest in a series of photographs of the Columbia taken by an amateur astronomer in San Francisco. Anne Stark, a spokeswoman for the Lawrence Livermore Laboratories, said NASA dispatched Tamara E. Jernigan, a former shuttle astronaut who flew three missions on the Columbia, most recently in 1996, to retrieve the pictures.

Ms. Stark said the photographs were taken with a digital camera on a tripod. One appeared to show some kind of purplish bolt from the sky intersecting with the shuttle. It was unclear what might have caused the bolt, or even if it was because of a defect in the camera, but Ms. Stark said NASA was eager to examine the images.

''She has handed over the photos to NASA,'' Ms. Stark said of Dr. Jernigan, who works at the Livermore lab. ''She told me, 'I think they are going to be really interested in looking at them.' ''

With new reports of possible debris surfacing daily, there was some confusion about which leads might be legitimate.

''I know of one call reporting a sewage pipe,'' said Catherine Unger of the San Jose Police Department. ''It seems everybody wants to be in on it.''

The E.P.A. announced today that the debris team would focus on nine locations in California, but the local authorities in several of them, including Los Angeles and Thousand Oaks, said they had received no reports of debris.

In other instances, some local authorities said they had heard directly from NASA that investigators would collect debris from them, but those locations were not listed by the E.P.A. as sites to be visited. Ms. Gentile, an E.P.A. spokeswoman, said some information about the team's activities was being kept confidential.

''They don't want anyone to hinder the investigation,'' she said.

In one report of debris, a rancher near Yosemite National Park found a piece of insulation, about six inches by eight inches in size near his swimming pool in Big Oak Flat, Calif.

The rancher, Gary G. Rolfe, said he had heard a sonic boom when the shuttle passed overhead on Saturday morning, but had not considered the foam might be related to the disaster until news reports suggested the spacecraft could have broken apart over California.

''We are way up in the mountains on 1,200 acres,'' Mr. Rolfe said. ''You don't normally find things like this tucked between the pine trees.''

In Santa Cruz, a woman walking the beach on Tuesday found a octagonal metallic object about 15 inches long. It had hash marks on it with a series of numbers spaced every inch, said Alex K. Peabody, the lifeguard supervisor for the area.

Mr. Peabody retrieved the object and said he recorded the latitude and longitude of the finding, which were of interest to NASA.

''It looks like it has a scorched mark on one side,'' he said.

In Southern California, the San Bernardino County Sheriff's Department said NASA investigators were on their way to secure a charred metallic object found in Joshua Tree.

Cindy Beavers, a spokesperson for the department, said Bob Beggs, a Joshua Tree resident, pulled into his driveway on Saturday afternoon and inadvertently ran over a small object The object is approximately the size and width of a credit card, with small numbers around a hollow center with burned edges and a foil covering on one side.

Mr. Beggs, 39, said that when he picked up the item at first, it had a center of solid black carbon. An official was dispatched to Mr. Beggs' home and packaged the object in a plastic bag. NASA contacted the sheriff's department today, telling officials there that investigators would collect the object.

''They're definitely interested in it,'' Ms. Beavers said. ''But they're so overwhelmed, we don't know exactly when they'll come take possession of it.''