NASA sent a team to California Wednesday to inspect material that might be part of one of Columbia's wings. While NASA cautions it is still weeks or months from unraveling the events that led to Saturday's accident, early attention has focused on the left wing and when precisely in the ill-fated flight material began to break off the shuttle orbiter.

The space agency also sent a military helicopter Wednesday to recover the damaged nose cone of space shuttle Columbia, which measures 4 feet across, from an east Texas forest. The nose cone was first discovered on Monday near Hemphill, Texas by two men looking for wreckage.

As shuttle fragments and body parts continue to turn up in Texas and Louisiana, NASA has recovered more than 12,000 remnants. NASA officials predict it could take months or years to pick through the pieces and begin the process of reassembling.

Michael Kostelnik, NASA's deputy administrator for human space flight, said the space agency had not determined whether the material found in California is from Columbia's wing - or even from the shuttle at all. "Debris early in the flight path would be critical because that material would obviously be near the start of the events" that unfolded during the shuttle's west-to-east trip across the country, Kostelnik said.

Meanwhile, NASA is focused on defending the shuttle's thermal tile system, which has come under fire recently after it was reported that a technical report warned at least nine years ago that the heat-protection tiles on the undersides of the shuttle's wings were susceptible to damage that could destroy the spacecraft. This currently is one of the leading theories behind the Columbia disaster.

A technical report published in 1990, with a follow-up paper published in 1994, by Paul Fischbeck, an engineering professor at Carnegie Mellon University, stated that the shuttle was vulnerable to tiles being knocked off or broken by insulation falling from the fuel tank and from other debris. Specifically, Fischbeck wrote: "fifteen percent of the tiles contributed to 85 percent of the risk." In his analysis, he recommended: "NASA inspect the bond of the most risk-critical tiles and reinforce the insulation of the external systems (external tank and solid rocket boosters) that could damage the high-risk tiles if it debonds at take-off."

Also today, additional human remains of the seven astronauts were recovered and are being transported to Dover Air Force Base in Delaware. The remains of Israeli air force Col. Ilan Ramon will be returned to Israel for burial, the Israeli military said.

President Bush on Tuesday paid tribute to the seven astronauts who lost their lives at a memorial service at the Johnson Space Center in Texas. He promised that the exploration of space would continue, despite the Columbia disaster.

Special Report: Columbia Disintegrates