Police divers have been deployed in the search for Brian Laundrie in a vast reserve near his family’s home in Florida.
Ten divers from the Sarasota County Sheriff’s Office arrived on Wednesday to join a multi-agency search of the Carlton Reserve.
They joined more than 50 officers from the FBI, several police departments in the search of the 25,000-acre Carlton Reserve which began on Saturday.
Law enforcement agencies are also using drones, a canine unit and all-terrain vehicles in their search of the “vast and unforgiving” swampland, which is largely underwater and infested with snakes and alligators.
The dive unit was requested by North Port Police on Wednesday morning, who said while nothing had been found, but they had to rule out the possibility of Mr Laundrie being in the water.
“These divers are specifically trained and very talented in low visibility bodies of water,” Sarasota County Sheriff’s office spokesperson Kaitlyn Perez told CNN.
“They dive down where you and I can’t see anything at all. They utilise technology and other special equipment to help them get down deep into really deep bodies of water, so they’re out there right now to recover whatever it is that they might find.”
Mr Laundrie, 23, has not been seen since leaving his family home in North Port last Tuesday.
He was declared a person of interest in the disappearance of his girlfriend Gabby Petito, 22, the next day.
Authorities launched a search for Mr Laundrie on 17 September after his parents notified them he was missing.
Ms Petito’s remains were found in the Bridger-Teton National Forest in Wyoming on Sunday.
The Sheriff’s Underwater Recovery Force (SURF) is a team of “highly trained underwater specialists,” who are “called upon to search for evidence of crimes and victims of drowning, water accidents and foul play,” the sheriff’s department website says.