Kennedy Space Center-AP -- A leading theory on the cause of Saturday's shuttle disaster -- the thermal tiles damaged during liftoff. NASA officials emphasize it's too soon to say for sure. An engineering report issued during Columbia's flight concluded that damaged tiles were not a hazard.(Nacogdoches, Texas-AP) -- The search for pieces of the space shuttle Columbia has expanded westward. The salvage operation covers an area from the hills of East Texas to a suburb of New Orleans. In East Texas, authorities are combing dense forest and divers are searching the bottom of Toledo Bend Reservoir. (Bethesda, Maryland-AP) -- President Bush is praising the space shuttle Columbia's seven astronauts for "their achievements, their heroism and their sense of wonder." Bush today told workers at the National Institutes of Health that the shuttle's loss is a reminder of the sacrifices that often accompany scientific learning. (Undated) -- The families of Columbia's crew are urging the nation to continue "the bold exploration of space." Relatives of the crew members issued a statement after getting together yesterday. Commander Rick Husband's widow, Evelyn, says the families gained strength from each other. (Capitol Hill-AP) -- Congress will take its own look at the space shuttle program following the Columbia disaster. Senate and House leaders say lawmakers will invite NASA to testify about the cause of the accident. And legislators will review the role of the shuttle in future space exploration. (Washington-AP) -- President Bush has sent Congress a budget with record-high deficits over the next two years. The two (t) trillion dollar spending plan would accelerate tax cuts, overhaul social programs, give NASA a modest increase and shower (b) billions on defense and homeland security. Copyright 2003 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.