WASHINGTON (AP) — After digging in the rubble and searching for victims at the Pentagon for nearly a week, some of the exhausted search and rescue crews are being sent home.

"It's tough to walk away," Tom Carr, leader of the Montgomery County, Md., task force, said Monday.

Teams from Fairfax County, Va., and Montgomery County — suburban Washington, D.C. communities that were first on the scene after the hijacked airliner crashed Sept. 11 — were being replaced by a search and rescue unit based in Albuquerque, N.M.

That western team will join teams from Tennessee and Virginia Beach, Va., bringing the total number of crews to three.

"We have accomplished a lot of work and because of that we've been able to downsize the number of people we need here," explained John Huff, the Federal Emergency Management Agency's incident support team leader for the search and rescue task forces.

Huff said crews had made progress in clearing debris from the impact area where the roof of the Pentagon's outer ring collapsed, and in stabilizing much of building.

Aiding their efforts was a colossal piece of machinery crews nicknamed "T-Rex." The pulverizer crushes chunks of concrete and rebar into smaller pieces to be hauled off. Before and after the debris is smashed, FBI and local police go through it, searching for evidence.

Despite the progress, officials cautioned the operation is far from over.

"This event is probably one of the worst things you can imagine as a rescuer because you have a structural collapse, a building fire and a plane crash all rolled up into one event," Huff said.

Crews will continue to pick away at the main rubble pile, shoring up sections of the building and searching for victims.

Of 188 victims, Pentagon officials said the remains of 97 people had been removed by Monday. Eleven of those have been identified.