WASHINGTON — Stored in such places as the vacant land near an airfield in Hope, Ark., an industrial park in Cumberland, Md., and a warehouse in Edison, N.J., are the results of one of the federal government’s costliest stumbles in the aftermath of Hurricane Katrina — tens of thousands of empty trailers.

The Federal Emergency Management Agency hurriedly bought 145,000 trailers and mobile homes just before and after Katrina hit, spending $2.7 billion largely through no-bid contracts. Now, it is selling off as many as 41,000 of the homes, netting, so far, about 40 cents on each dollar spent by taxpayers.

Thousands more of the homes — critics say more than 8,000 — have never been used and cannot be sold immediately, even though scores of people in the South have been made homeless by recent storms.

“While FEMA has 8,420 brand new, fully furnished, never-used mobile homes in a cow pasture in Hope, Ark., they refuse to provide the people from Desha, Back Gate, and Dumas counties with help. This is crazy” Rep. Mike Ross, a Democrat of Arkansas, said. “If this is the new and improved FEMA, I don’t want any part of it.”

FEMA cannot sell unused mobile homes directly to the public because of legislation passed by Congress in October at the industry’s urging. Instead, the agency must now go through a time-consuming process of trying to donate them first to federal, state, and local agencies and public service groups, according to the Manufactured Housing Institute’s Web site.

But FEMA has refused Mr. Ross’s request to release 150 mobile homes to shelter people in his state displaced on February 24 by two tornadoes because President Bush has not declared the counties a federal disaster area, precluding FEMA’s involvement.

Still, the number of homes the agency can sell is prompting fears of a market glut. FEMA’s potential for-sale inventory is nearly equivalent to 30% of the recreational-vehicle industry’s American sales in 2006.

“As you can imagine, a public auction of so many vehicles could devastate the market for travel trailers,” the president of the 2,700-member Recreational Vehicle Dealers Association, Michael Molino, said in a letter Friday to the director of FEMA, R. David Paulison.

Mr. Molino’s group and the National Association of RV Parks & Campgrounds last week asked that the trailers be sold in lots of five or more so they can be bought and resold by dealers. Both groups said selling directly to individuals could pose safety hazards if adequate training is not provided.