Houston ? A breach in Columbia’s skin allowed glowing, superheated air to penetrate the space shuttle, possibly in its left wheel well, seconds before the craft broke apart over Texas, killing its seven-member crew, investigators said Thursday.

In its first key finding, the independent board said the shuttle fuselage sustained a significant rupture, rather than simply incurring damage from the loss of a few heat-resistant tiles or another internal malfunction.

National Aeronautics and Space Administration officials now suspect that plasma — air heated to temperatures exceeding 2,000 degrees — penetrated the shuttle’s armor through the leading edge of the left wing or through a 300-pound landing gear door, sheathed in protective tiles. Either way, one NASA consultant said Thursday night, “that’s death.”

The finding supports a scenario that NASA was warned about in a 1994 report by two researchers at Carnegie Mellon University and Stanford University, who said debris on launch could cause enough damage to tiles to cause a loss of the orbiter on re-entry.

The announcement renewed debate about the potential damage caused when a piece of foam insulation fell from an external tank during liftoff and struck the left side of the shuttle.

Portions of the space shuttle that encounter the highest temperatures are covered with about 24,000 tiles that typically protect it against the heat. If a patch of those tiles fail — or if the plasma finds another way inside — it would mark the beginning of a devastating chain reaction.

The board’s statement came hours after NASA officials conceded they failed to act on their own engineer’s suggestion that they use a sophisticated flight simulator to test the shuttle’s ability to fly if it was severely damaged by the insulation. A NASA engineer suggested those tests two days before the Feb. 1 destruction of the Columbia.