More than three weeks into the search for missing British woman Sarm Heslop in the U.S. Virgin Islands, police have announced little progress in the case -- and they haven't gone inside the yacht where she was last seen.

Heslop, 41, was last seen on her boyfriend Ryan Bane’s catamaran, the Siren Song, on March 8, although police have not said conclusively if and when she returned to it that night. The couple was seen in public together hours earlier, leaving a bar and restaurant around 10 p.m.

Bane reported her missing around 2:30 a.m.

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The mystery comes as U.S. Virgin Islands authorities are cracking down on a spike in violent crime.

In October 2020, U.S. Attorney Gretchen Shappert’s office announced it was stepping up federal efforts to combat violent crime after an increase in homicides across the territory.

And the U.S. Virgin Islands Police Department currently lists 23 active missing persons cases on its website, including Heslop’s.

Jerry Forrester, a former FBI agent and private investigator who has worked extensively in the Caribbean, said the number of missing people is unusually high for the U.S. Virgin Islands’ population of just over 100,000 – but he also noted that investigators don’t assume all of those missing are dead.

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"That’s a lot for that hundred thousand people, but they aren’t that concerned about it are they, the police?" he told Fox News Wednesday. "Maybe there’s a reason they’re missing, not dying. Maybe they just left. They moved somewhere else or they just wanted to get lost somewhere. But there’s no proof that they were killed."

Still, he said it seemed "not normal" that local police had not searched Bane’s boat – where Heslop was last believed to have been seen alive.

"Get a warrant, get a judge to sign the warrant and get a search warrant," Forrester said. "They have enough probably cause, I think. She’s missing, and she was on that boat. ... They’re just not doing their job."

The U.S. Virgin Islands Police Department did not immediately respond to requests for comment, but earlier this week investigators renewed their appeal for anyone with information on Heslop’s whereabouts to contact them. The FBI is also involved in the search, and police at the nearby British Virgin Islands told Fox News last week they were monitoring the case.

Bane has not been named a suspect or person of interest in Heslop’s vanishing, and police said he declined to let them search the Siren Song and hired a high-powered lawyer.

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The easily accessible water can be linked to many disappearances – where victims may have drowned accidentally, been injured or killed by forces of nature, Forrester said.

"There’s so many things that can happen to you," he said. "I just don’t believe that [all of] the people who are missing are missing because they all got killed."

But foul play does happen.

Stretching back to the mid-1970s, he said, he’d heard of at least three cases where a husband killed his wife by unplugging her oxygen supply while scuba diving in various parts of the Caribbean. But those cases are rare and hard to prove, he said.

There have also been, on rare occasions, deadly encounters with modern day pirates, he said.

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And local police may lose interest in missing persons cases over time, according to Forrester.

"If it’s open for a while, they’re not gonna solve it," Forrester said. "Unless somebody confesses."

Still, he said, he considered the region "fairly safe" for travelers -- and he's been working there for decades.