Mica, who has also berated GSA for several costly conferences the agency has held, vowed on Monday to keep holding these hearings as a way to draw attention to the money GSA has spent just to maintain empty buildings.

"If we have to have a hearing at every empty building in the country in order to get GSA to stop wasting money, we will do so," Mica said in Florida. "With 14,000 excess federal properties, this is four down and 13,996 to go.

GSA clarified this week that the 14,000 number is government-wide holdings of un-used property, and that GSA only controls 124 of these. GSA begins to manage these properties only after other agencies say they are ready to be sold.

Still, Mica said these properties need to be reduced regardless of who controls them, and blamed GSA for controlling most of these properties.

"GSA is notorious for its Vegas hot-tubber, junkets to the South Pacific and ludicrous bonuses that cost millions of dollars, but this agency and the federal government waste billions of dollars sitting on empty and underused buildings," Mica added.

Mica said his hearings have so far appeared to force GSA to speed up its own internal processes to find private buyers for some of the buildings. Mica said committee hearings on the Old Post Office Annex and other properties in Washington, D.C., led GSA to announce plans to use or sell these properties, and GSA announced just before Monday's field hearing that it is working on new plans for that courthouse in Miami.

— This story was updated Wednesday.