(CNN)-San Francisco (CNN) -- The U.S. Coast Guard is suspending its search off the California coast for a distressed 29-foot sailboat that was carrying a couple and two children, and said Tuesday the incident is "possibly a hoax."
The mission's cost has reached several hundreds of thousands of dollars since Sunday, said Cmdr. Don Montoro.
Searchers have been scouring the water off San Francisco for the people that a distress call claimed were on the boat: the couple, their 4-year-old child and the child's cousin, who the Coast Guard said was younger than 8.
Coast Guard investigators will look into the incident and "prosecute it and investigate it to the best of their ability," Montoro said. "We're not investigating it directly as a hoax, but we are pursuing every avenue. It's certainly a possibility."
"I know we do have successful prosecutions" on such hoaxes, Montoro said, "and it would be taken very seriously."
Since last June, the Coast Guard has been offering a $3,000 reward for information leading to the arrest and prosecution of those responsible for an apparent hoax that prompted a massive rescue effort off the coast of New Jersey following a distress call.
In that incident, a search came up empty for purportedly injured and adrift passengers from a yacht hit by an explosion at sea.
The agency found no evidence of people, debris or even a boat, it said. The investigation is still active, Coast Guard spokesman Charles Rowe said Tuesday.
Making a false distress call is considered a felony, punishable by up to 10 years behind bars and a $250,000 fine, the Coast Guard said last June. The person responsible could also be required to reimburse the government for the cost of the search.
In 2011, the Coast Guard counted 54 probable hoaxes nationwide out of 7,274 mayday cases, Rowe said. One hoax cost the Guard $74,000, another $44,000 and another $5,200, he said. Those costs don't include local police or other first responding agency costs, he added.
In one region alone -- New York City, Hudson River and northern New Jersey -- there were 80 probable hoaxes during the past six years, Rowe said.
In this week's incident off the California coast, the weather offshore during the search featured gale-force winds and 25-foot seas, Montoro said.
On Sunday afternoon, the Coast Guard received a radio communication that stated: "This is the Charm Blow, we are abandoning ship."
The man on the radio told the Coast Guard that the boat had begun taking on water and its electronics were failing, the agency said. At that time, the boat was believed to be some 65 miles (105 kilometers) off Pillar Point, south of San Francisco.
The focus of the search had been 60 to 65 miles off Monterey Bay, said Lt. Heather Lampert, a Coast Guard spokeswoman.
At 20,000 square miles, the search area was nearly the size of West Virginia.
The U.S. Navy from Point Magu and the 129th Air National Guard from Moffett Airfield participated in the search, Montoro said.
More than 40 search-and-rescue assets were involved in the effort, he said. At one point, two Coast Guard cutters, HC-130 planes, MH-65 helicopters and a Navy E2-C Hawkeye were involved, the Coast Guard said on Monday.
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