The FBI is assisting with the search of the Carlton Reserve outside of the city of North Port.
Mr Laundrie’s family told police they believe he entered the area earlier this week and have not seen him since Tuesday.
North Port Police announced the search in a tweet on Saturday morning.
The Carlton Reserve is home to feral hogs, alligators, and panthers, and has 80 miles of hiking trails. A warning on the park’s website says that most of the trails are currently flooded.
Mr Laundrie, who had been named as a person of interest following his fiancee’s disappearance, had refused to speak with police after returning alone from the couple’s road trip across the US.
He has not been seen for several days, according to his attorney, who informed authorities that his family had not seen him since Tuesday.
“The attorney for the Laundrie family called FBI investigators Friday night, indicating the family would like to talk about the disappearance of their son. The family now claims that they have not seen Brian since Tuesday of this week,” North Port Police public information officer Josh Taylor told the New York Post.
In a statement sharing a photograph of Mr Laundrie and requesting information as to his whereabouts, police said they were now conducting multiple missing persons investigations regarding Mr Laundrie and Ms Petito and that while he was a person of interest in his fiancee’s disappearance, he was not wanted in connection with any crime.
“We understand the community’s frustration, we are frustrated too,” North Post Police Department said.
Mr Laundrie returned home alone on 1 September from the couple’s cross-country van trip. Her parents reported her missing 10 days later.