Dental records show that the human remains found at a Florida wilderness park are those of Brian Laundrie, Gabby Petito’s fiance.
The 23-year-old had been named a person of interest in the killing of Ms Petito, who was reported missing on 11 September by her parents while the couple were on a road trip.
The FBI said the human remains were uncovered in the Carlton Reserve, Florida, in a location that was previously underwater.
His personal belongings – such as a notebook and backpack – were discovered nearby on Wednesday, where authorities were searching for Laundrie.
Ms Petito’s body was found on 19 September on the edge of Wyoming’s Grand Teton National Park, which the couple had visited.
A coroner concluded that she had been strangled and that her body had been there for three or four weeks.
Ms Petito’s case has generated huge public interest but also raised uncomfortable questions over the unequal attention given to the hundreds of cases of Native American and other minority women missing or murdered across the US. Ms Petito is white.
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The couple were stopped on 12 August by police in Moab, Utah, after they had a physical altercation, but no charges were filed.
Laundrie returned home alone on 1 September in the Ford van the couple took on their trip.
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He was reported missing after telling his parents two weeks later that he was going for a hike in the Carlton Reserve, a vast nature preserve that has for weeks been a key area in the search.
The activity on Wednesday was focused on the nearby Myakkahatchee Creek Environmental Park, where television news reports showed numerous law enforcement vehicles arriving and a tent set up inside the woods.
The location is where a Ford Mustang that Laundrie drove to the wilderness was discovered.
Laundrie had been charged in a federal Wyoming indictment with unauthorised use of a debit card, which would have allowed authorities to arrest him if had been found alive.
It alleged that Laundrie used a Capital One Bank card and someone’s personal identification number to make unauthorised withdrawals or charges worth more than $1,000 (£725).
It did not say to whom the card belonged or what type of charges were made.