As the search for debris of the U.S. space shuttle Columbia continues, the agency?s investigators may be close to finding the possible cause of the shuttle?s accident in February. Auria Aguilar-Makki has the latest on the investigation.

More pieces of shuttle debris arrived this week at the Kennedy Space Center, where engineers are working on reconstructing the space shuttle as part of the investigation. NASA estimates it already has collected more than 75 thousand pieces of debris. It expects to recover 40 percent of the shuttle when the search comes to an end in about three to four weeks.

Meanwhile, investigators are now looking at damage on the shuttle?s left wing as an important factor in the crash. After analyzing images recorded during lift-off, they believe a slit opened in a seal along the left wing. The seal is close to where investigators believe a chunk of foam insulation hit the wing.

Scott Hubbard, a high-ranking NASA official on the investigating board, says tests will be conducted at what engineers call the ?T-seal? on a prototype shuttle:

?In the preliminary planning for the impact tests, we are putting strong consideration on hitting not the middle of the panel, but that intersection where the T-seal is, and seeing what happens, what kinds of damage will be caused.?

Officials say the new impact zone is based on camera views of the tumbling debris. Information from a recovered data recorder shows an increase in temperature at that location, eight minutes after Columbia entered the atmosphere.

Retired admiral Harold Gehman, chair of the Columbia Accident Investigating Board, said he will release recommendations for NASA this week. The board will urge NASA to adopt better methods for testing age-related damage in wing panels, seals and other shuttle parts, as well as to routinely photograph orbiting shuttles for possible damage.