From an AP report:

SPACE CENTER, Houston, Feb. 1 — NASA declared an emergency after losing communication with space shuttle Columbia as the ship soared over Texas several minutes before its expected landing time Saturday morning.

FEARING THE WORST, NASA ordered flight controllers to pull out emergency procedures and ordered them to retain all their records.
Columbia was aiming for a touch down at 9:16 a.m.
It was at an altitude of 200,700 feet, traveling at 12,500 mph when mission control lost contact. There was no further communication and no further tracking data.
Reporters at the landing strip were ordered away 7 minutes after the scheduled touchdown with still no sign of the shuttle.
In 42 years of human space flight, NASA has never lost a space crew during landing or the ride back to orbit. In 1986, space shuttle Challenger exploded shortly after liftoff.
Security had been tight for the 16-day scientific research mission that included the first Israeli astronaut.
Ilan Ramon, a colonel in Israel’s air force and former fighter pilot, became the first man from his country to fly in space, and his presence resulted in an increase in security, not only for Columbia’s Jan. 16 launch, but also for its landing. Space agency officials feared his presence might make the shuttle more of a terrorist target.
On launch day, a piece of insulating foam on the external fuel tank came off during liftoff and was believed to have struck the left wing of the shuttle. NASA said as late as Friday that the damage to the thermal tiles was believed to be minor and posed no safety concern during the fiery decent through the atmosphere.