The controversy over the biggest dump for Hurricane Katrina debris got a lot messier with a lawsuit claiming the city and the landfill’s operators illegally used private land.

The suit is the latest in the saga of the Old Gentilly Landfill, an old municipal dump the city rushed to reopen to hold all the debris from the 2005 storm.

The lawsuit, filed Wednesday, alleges that the city and the landfill’s operator illegally dumped 10 million cubic yards of waste _ enough to fill half the Louisiana Superdome _ on land that neither owns. Attorneys hope to make the case a class-action suit.

Dozens of individuals and entities claim they never gave the city permission to dump on their land and never got a dime for all the waste that’s now piled there, according to the lawsuit.

“I think I have four lots out there that was purchased more or less as investment property,” said Doretha Z. Walker, a 77-year-old retiree who worked for the New Orleans musicians’ union. “I had no idea they were using it for a landfill.”

The dump was originally opened in the 1960s and closed in 1982. Many property owners bought the land decades ago when it was still undeveloped swamp. Since then, many sections have been developed and there are several roads through the area. The state approved a permit to reopen it as a dump shortly after Katrina hit.

Joel Waltzer, one of the lawyers who filed the suit, said he discovered the landfill was allegedly atop private land while he was studying the area.

The landowners should be compensated for the damage to their property and get a share of the landfill’s past and future profits, the suit contends.

Donald Trahan, an attorney supervisor at the Louisiana Department of Environmental Quality, said the state trusted that New Orleans owned the land.

Mayor Ray Nagin, the city attorney and the landfill operators _ AMID/Metro Partnership LLC _ did not return telephone calls seeking comment.