MILTON, Fla. - Wildlife officials say they're puzzled by what sickened six bald eagles in the Florida Panhandle after months of investigation.

The mystery began in late February, when a state worker found four of the birds - two dead, two seriously ill - near the Central Landfill in Milton. Two other sick eagles were found later nearby the landfill.

Investigators with the Florida Fish and Wildlife Conservation Commission and the U.S. Fish and Wildlife Service have been on the case ever since, but a reason for the illnesses remains elusive.

"It's one of the more puzzling cases I've ever worked on," FWC Investigator Jerry Shores said.

Shores said tests found all of the birds suffered from severe food poisoning, which is unusual for the species. Initial speculation was that the eagles were intentionally poisoned, and officials still haven't ruled that possibility out, but analysis of the birds' blood has so far failed to produce any tell-tale signs.

"There's no smoking gun," Shores told the Pensacola News Journal (http://on.pnj.com/1vkBhGa ). "We're kind of at a standstill."

The two dead birds have been taken to a U.S. Fish and Wildlife Service lab in Oregon, where they are awaiting necropsies. It could be months before the state receives results.

"Were hoping that that will give us the smoking gun as to why they've died," Shores said.

The four sick birds have all recovered and are at area wildlife refuges.