POMPANO BEACH, FL -- Two small planes collided over the Everglades Saturday, crashing into the swam. Authorities say there were likely no survivors.

A Piper aircraft and another plane believed to be a Cessna crashed at about 3 p.m., Federal Aviation Administration spokeswoman Kathleen Bergen says.

Authorities believe there was only one person on board the Piper. They were still determining how many people were on the second plane.

The area where the planes went down is only accessible by airboat, and the wreckage quickly sunk, says Palm Beach County Fire-Rescue Capt. Don DeLucia.

There were no survivors, DeLucia says, although no bodies had yet been recovered.

"They're in the water, under the water," DeLucia says. "We have no idea how many victims there are. It could be as few as two, or more."

He says the recovery effort would continue until dark, then resume at daybreak.

"They're all out there on airboats searching now," DeLucia says. "It's going to get pretty dark out here soon. We're talking about the swamp out here."

A sheriff's helicopter would use a heat sensor to search the area Saturday evening just in case someone survived and was hidden in the sawgrass, says Palm Beach County sheriff's Sgt. Pete Palenzuela.

The Piper was registered to Harry Duckworth of Waverly, PA, and was en route from Ocala to Pompano Beach, according to FAA records of the flight plan.

A telephone message left by The Associated Press for a Harry Duckworth in Waverly was not immediately returned Saturday evening. Bergen warns that Duckworth was not necessarily on board.

Bergen said the second plane didn't file a flight plan. Authorities on scene had retrieved the tail numbers and were contacting the owners, Palenzuela says.

The planes collided about 14 miles northwest of Pompano Beach in southeast Florida.