With underwater dive teams called in to join the search in Florida's Carlton Reserve for Brian Laundrie, who has been missing for more than a week, experts fear police may have fallen for a "red herring".
The search for the 23-year-old, who is a "person of interest" in the disappearance and death of his fiancee Gabby Petito in Wyoming, resumed today (Wednesday morning local time) and is still, after four days, focused around the alligator-infested reserve.
When his parents, Christopher and Roberta, told police on September 17 their son was "missing" after going on a hike three days prior, the 10,000ha reserve has become the scene of an ongoing land and air search for Mr Laundrie.
The three-day lead Laundrie had before being reported "missing" to police in itself presents a disadvantage for authorities. But with extensive efforts concluding each day with empty hands, a search-and-rescue expert claim Laundrie may have lied to his family about his whereabouts and "could be almost anywhere".
Speaking to Insider, Chris Boyer, the executive director of the National Association for Search and Rescue, said Laundrie's location could have "used" those closest to him to make a getaway.
"People that are trying not to get caught for something sometimes use people, right? So he may have told his parents that's where he's going," Mr Boyer said.
"They may be telling the authorities that in all honesty, but he lied to them."
Boyer said that while search efforts remain in Carlton Reserve, where Laundrie also left his silver Ford Mustang, the 23-year-old could be "anywhere" by now.
"There's any number of ways that he could have hitchhiked or somehow found a collaborator to give him a ride somewhere," he said.
"He may not even be in Florida. He's had eight days to be on the run right now. He could be almost anywhere."
While Laundrie has not be charged with a crime, he was named by police and the FBI as a person of interest in the missing-person case of Petito.
After an extensive land and air search of Grand Teton National Park in Wyoming, the young blogger's remains were found on Sunday local time.
Two days later, an autopsy has revealed the 22-year-old was likely murdered.
Teton County Coroner Dr Brent Blue said the initial autopsy was finished, confirming the remains found were of Petito and her manner of death was likely homicide. The cause was still to be determined.
Police involved in the Carlton Reserve search have previously warned of the "very difficult" terrain they face.
With alligator and snake-infested swampy conditions – and with the investigation complicated by Laundrie having several days to get ahead of them – "the search area gets bigger every hour you don't find him".
"It's not that hard to hide from ground searchers that are just using their Mark I Eyeball," Boyer added, using a military term that means naked eye.
"[It's] pretty easy in that swamp, especially if you're wearing clothes that blend in with the environment and don't provide any contrast."
The North Port Police Department, which is assisting the FBI with what's now a criminal investigation, said that the vast nature of the reserve has clearly presented challenges.
"Terrain's very difficult. Essentially, 75 per cent of it's underwater, and other areas that are dry we're trying to clear," North Port Police Commander Joe Fussell said on Tuesday.
"So we're expecting to get wet by the end of the day and check the entire area for Brian Laundrie."
Appearing on CNN, former America's Most Wanted host John Walsh said: "My philosophy is, he never went to the swamp. He believes searchers are wasting their time looking in the reserve, which he claimed could be a "red herring".
Experts say with the right know-how, supplies and experience, Laundrie could last a "pretty long time" in the unforgiving wilderness.
"Look at that Olympic bomber [Eric Rudolph]," Boyer explained, referring to the man behind the 1996 Atlantic Olympics bombing attack who hid out for five years in the Appalachian wilderness.
"You can live a long time in these conditions, depending on what you pack with you, but eventually, he'll have to come out for supplies – maybe he has a medical emergency, maybe he's just interested in what's happening because he's so cut off from the world."