Brian Laundrie, 23, returned home alone one month after setting out in a van on a cross-country adventure with Ms Petito, 22.
A body discovered over the weekend at a US national park in Wyoming was found to be “consistent with the description” of the missing blogger, FBI agents said.
On Monday, the FBI issued a search warrant at Mr Laundrie’s Florida home.
His parents were removed from the property, according to local media reports.
Footage showed at least a dozen officers pulling up to the house in North Port.
Mr Laundrie and Ms Petito hit the road in July in a converted van to visit national parks in the West.
He was alone when he returned in the van to his parents’ home on September 1, according to police.
Now Mr Laundrie has been named a person of interest in the case but his whereabouts in recent days were unknown.
In Wyoming, the FBI announced on Sunday agents had discovered a body while searching campsites on the edge of Grand Teton National Park where the couple had visited.
No details on the cause of death were released and an autopsy was set for Tuesday.
FBI agent Charles Jones said: “Full forensic identification has not been completed to confirm 100 per cent that we found Gabby but her family has been notified.
“This is an incredibly difficult time for family and friends.”
Ms Petito‘s father Joseph shared a broken heart alongside a picture of his daughter. His message read: “She touched the world.”
A lawyer acting as a spokesperson for Ms Petito‘s family asked they have room to grieve.
Investigators have been seeking information from anyone who may have seen Ms Petito or Mr Laundrie around Grand Teton.
A weekend search of a Florida nature preserve failed to find Mr Laundrie, according to officers.
North Port police said they “exhausted all avenues in searching the grounds” of the 24,000-acre Carlton Reserve in Sarasota County.
The area became a key focus after Mr Laundrie’s parents told police he may have gone there.
Ms Petito and Mr Laundrie were childhood sweethearts who met while growing up on New York’s Long Island.
His parents later moved to North Port, about 35 miles south of Sarasota.