Searchers from several counties have battled the heat and encountered everything from snakes to black bears, but they haven't found a clue to the disappearance of a husband and wife.
Jack and Patricia Doyle were last seen June 13, apparently returning to the 5,600-acre ranch belonging to Mrs. Doyle's parents from DeLeon Springs.
Family members have posted a $5,000 reward for information.
Volunteers and law officers on foot and using all-terrain vehicles, horses, canoes and helicopters had turned up nothing by late Monday.
"We feel, at this point, foul play is involved," Gary Davidson, a Volusia County sheriff's spokesman, said Sunday. "Too much time has transpired."
"There is no indication that they left on their own or that they left on some planned trip," he said. "Luggage, personal belongings, were left behind."
The couple's credit cards and bank funds have not been touched since they disappeared.
Searchers have turned up no trace of the couple's red 1986 four-door Isuzu Trooper. Its license plate is PSR 10T.
Doyle, 62, a retired lawyer, and his wife, 59, moved to Florida from California a year ago to care for Mrs. Doyle's parents, Theodore and Althea Strawn.