SANDY HOOK, N.J. – The U.S. Coast Guard said a reported explosion on a motor yacht off central New Jersey likely was a hoax, and an extensive search and rescue operation cost hundreds of thousands of dollars.

An investigation has begun to determine who was responsible, and the agency is offering a $3,000 reward for prosecution of the person responsible.

The multiagency mission was launched after authorities received an emergency radio transmission around 4:20 p.m. Monday from a boat identifying itself as the Blind Date. The caller reported the boat was 17 nautical miles east of Sandy Hook, had 21 people aboard and several people injured.

The caller also claimed the vessel sank, but everyone aboard had made it to life rafts. But Coast Guard crews and New York City police helicopters found no sign of any people or any distress in the water, and after two hours of searching it became increasingly clear there was no explosion.

About three hours on, emergency crews began leaving the mass casualty staging areas that had been set up to receive the reported injured passengers, and nearly five hours after the distress call was received the Coast Guard confirmed it was likely a hoax.

Commander Kenneth Pierro of Coast Guard Sector New York said more than 200 first responders had assembled at the staging areas, and officials said several good Samaritans had assisted authorities in the lengthy search.

He noted that hoax calls put the Coast Guard and other first responders at unnecessary risk, and can interfere with the Coast Guard’s ability to respond to actual distress at sea.

Making a false distress call is a federal felony, with a maximum penalty of five to 10 years in prison, a $250,000 fine and reimbursement to the Coast Guard for the cost of performing the search. T

he Coast Guard and other state and local agencies responded to more than 60 suspected hoax calls last year in the northern New Jersey, New York City and Hudson River region.

Monday’s distress call and search came nearly a year after a similar situation unfolded near Sandy Hook.

A call on an emergency radio channel was received in the early morning hours of June 14, 2011, with the caller claiming a 33-foot sailboat named Courtney Lynn was taking on water. Less than an hour later, another call came in claiming the boat was 90 percent submerged, and the four boaters were transferring to a small gray dinghy.

No further transmissions were received from the callers, who said they didn’t have a handheld radio or flares to communicate with rescuers from the dinghy. A 10-hour search costing almost $88,000 turned up no sign of the boaters, and an investigation was launched. No one has been prosecuted.