One floor beneath the World Trade Center, in what used to be a shopping concourse, a clock on a jewelry store wall remained frozen at 9:10. A ghostly Bugs Bunny statue stood coated in gray dust outside a Warner Brothers gift shop nearby.

As the stores in the underground mall were checked one-by-one for survivors, rescue workers marked them with an orange X: They made one stroke of the X as they went in, the other as they came out.

Wearing what looked like miner's helmets, search crews from the Federal Emergency Management Agency picked through the rubble and the darkness under 5 World Trade Center on Tuesday, burrowing into any space big enough to shield a survivor. The nine-story section of the Trade Center was charred but did not collapse when the complex's 110-story twin towers crumbled on Sept. 11.

"There are caverns down here," said Don Schroeder, commander of a FEMA unit from Sacramento, Calif. "The focus is to continue to find and extract victims from a pile of rubble like this."

He said he had no doubt a person could have survived in the spaces the workers found, but nobody has been found alive so far. He said some bodies were recovered as crews tunneled into the concourse but could not say how many.

The mall was dark except for headlamp beams and some daylight that fell through the shaft of a stalled escalator. Broken glass crunched underfoot. The air was stale and stifling. Workers wore heavy, elaborate filter masks. Canisters of oxygen were on hand if needed.

At the Tourneau jewelry shop, where eight clocks displayed time from around the world, local time had stopped at 9:10 — about 22 minutes after terrorists began the attack by hijacked airplanes that brought down the towers.

The store's windows were shattered. Rolex boxes were empty. Pale blue velvet cushioning display counters was caked in dust.

The workers were from a FEMA Urban Rescue team based in Sacramento, Calif., one of eight 62-member teams on duty from California, Ohio, Indiana, Missouri, Florida and Pennsylvania.

They searched by hand through the corridors of the concourse, tossing aside rubble, peering into spaces and snaking in a fiber optic camera when they could burrow no farther. Harley, a golden retriever, helped sniff for victims.

Outside, the daunting rescue and recovery efforts continued in orderly fashion in the rubble of the towers. Cranes lifted large pieces of debris from a great crater. A large trash bin was labeled "AIRPLANE PARTS" in bright yellow spray paint.

Fliers were posted throughout the area, showing workers what an airliner's black box looks like. The black boxes of the two airliners that brought down the twin towers have not been found.

Hand-lettered signs in the windows above said "God Bless America," and "R.I.P." and "Kill Them All — Let Allah Sort Them Out."

Many of the rescue workers appeared weary. But a team of state troopers in crisp creased flannels monitored the perimeter, standing in puddles.

Above the entrance to 5 World Trade Center, where the FEMA team was working below, was a sign that said, "Open Every Day."