SANDY HOOK, N.J. -- The U.S. Coast Guard launched an investigation Tuesday into a possible hoax after a 10-hour search turned up no sign of four boaters who sent distress calls saying they were abandoning ship.

Boats, planes and helicopters were dispatched before sunrise in a rescue operation that joined together military, state and local agencies and cost the Coast Guard almost $88,000. The rescue was called off in the afternoon after a search of a 600-square-mile area failed to turn up a boat, debris or the sailors.

Authorities are searching for whoever made two false distress calls -- a federal felony -- and are offering a reward of up to $1,000 for information leading to arrest and prosecution.

The first call came in shortly after 3 a.m. Tuesday on an emergency radio channel. Claiming to be aboard a 33-foot white sailboat named Courtney Lynn, the callers said their vessel was taking on water. Less than an hour later, those aboard radioed that the boat was 90 percent submerged, and that they were transferring to a small gray dinghy.

No further transmissions were received from the callers, who said they didn't have a hand-held radio or flares to communicate with rescuers from the dinghy. The Coast Guard did not have information about boat registration or owners.

A Coast Guard boat searched for five hours, while local police agencies searched from land. A Coast Guard airplane was dispatched from Massachusetts and flew three rescue flights over the search area, while both the Coast Guard and New Jersey State Police searched by helicopter.

"The weather conditions were ideal for finding a 33-foot vessel, even if it were sinking," said Chief Warrant Officer Troy Loining, who commands the Coast Guard's Sandy Hook Station.

The initial distress call placed the boat to the east of a naval station and a few miles from Sandy Hook Bay, an inlet of the Atlantic Ocean between New York City and northeastern New Jersey. The crew later corrected their position to say they were west of the naval station. Coast Guard direction-finding equipment was used to determine the signal likely came from a few miles away near Highlands, N.J., south of Sandy Hook.

With all search options exhausted and no evidence of anyone in distress, the rescue was suspended around 1:40 p.m. and an investigation launched. Making false distress calls is a felony that can result in up to 10 years in prison and $250,000 in fines, according to the Coast Guard.

"False distress calls waste taxpayer dollars, put Coast Guard and other first responders at unnecessary risk and can interfere with the Coast Guard's ability to respond to those in actual distress at sea," said Coast Guard spokesman Charles Rowe.

Officials urged anyone with information to contact the Coast Guard anonymously at 646-872-5774.

Sandy Hook Station has responded to calls in the past that have turned out to be hoaxes, Loining said, but other distress calls have turned into legitimate rescues. In May 2010, the Coast Guard rescued two people by helicopter from a capsizing boat near Sandy Hook.