NASA QUESTIONED SHUTTLE TIRE SAFETY.(MAIN)

Byline: TED BRIDIS Associated Press

WASHINGTON -- NASA engineers questioned whether damage from extreme heat during Columbia's fiery descent could cause its tires to fail on the runway, despite assurances days earlier that possible damage to insulating tiles near the landing gear wouldn't imperil the shuttle's safe return.

Since Columbia's breakup over Texas, senior NASA officials have expressed repeated confidence in conclusions by engineers at Boeing Co., its contractor, that the shuttle could return safely despite the risks of damage to delicate thermal tiles on its left wing that might have occurred on liftoff.

In prepared testimony for a …