MIAMI (AP) — Millions of square feet of wasted space in federal courthouses that have opened since 2000 are costing U.S. taxpayers upwards of $51 million a year, congressional auditors reported Thursday.

The 33 courthouses, including the Ferguson Courthouse in downtown Miami, were overbuilt by more than 3.5 million square feet at an initial construction cost of $835 million, according to the study by the Government Accountability Office. That’s enough space for nine average-sized courthouses, the GA0 estimated.

Rent, maintenance and operation costs account for the $51 million in extra costs each year. And that amount will keep rising.

The study was released by a U.S. House Oversight and Government Reform panel that is scheduled to hold a hearing on the issue Friday in Miami. In addition to the extra space issue, Republican-controlled House committees have been investigating surplus and empty federal properties such as Miami’s historic Dyer Courthouse, which has been vacant since 2008.

The hearing on courthouse waste comes as Congress and President Barack Obama wrestle with how to handle $85 billion in mandated budget cuts that have stoked fears of government service cutbacks, worker furloughs and shuttered public properties.

U.S. Rep. John Mica, a Florida Republican who chairs the House subcommittee, said the hearing is aimed at shining a light on “this waste and unacceptable inaction.” He placed much of the blame on the GSA, which owns and oversees thousands of federal buildings across the country including the Miami courthouse that opened in 1933.

“For nearly six years, GSA has let this historic building deteriorate and ensure taxpayers are shortchanged while the country falls into financial ruin,” Mica said in an email.

GSA officials did not immediately comment Thursday. A regional GSA administrator is scheduled to testify at Friday’s hearing.

There are a number of reasons the newer courthouses were overbuilt, the GAO found. Some were constructed at a much larger size than authorized by Congress. In other cases, estimates were off on how many judges there would be in a given courthouse. In addition, many times there were no plans to have judges share courtrooms.

In the new Miami courthouse’s case, the GAO study showed that as of 2010 there were only 27 judges instead of the 33 that were originally projected. That resulted in 57,000 extra square feet of space including two courtrooms that have never been finished. There are also three other buildings — not counting the vacant Dyer courthouse — in Miami that contain federal courtrooms.

Last year, the GSA said it would ask developers and the business community for suggestions on what to do with the Dyer building. One proposal came from Miami Dade College, which has a large campus across the street and wants to use the old courthouse as an educational and cultural center.

The college’s president, Eduardo J. Padron, said in remarks prepared for Friday’s hearing that talks are “inching forward” with GSA on that idea, which would include preserving the building as a historic site.

“We propose a new chapter for this historic building that will be rich in promise for all,” Padron said. “We hope our federal partners will give us this chance.”