Human remains found in a Florida nature reserve belong to the boyfriend of murdered road tripper Gabby Petito, US authorities said Thursday.

The FBI said in a statement that "a comparison of dental records confirmed that the human remains... are those of Brian Laundrie."

Laundrie, 23, had been named a "person of interest" in the killing of Petito, 22, who was found dead in September after the couple went on a road trip across the United States.

Petito had quit her job in New York and packed her life into a camper van for a cross-country adventure with Laundrie over the summer, documenting their journey in a stream of social media posts.

In bodycam images from August 2021, Gabrielle Petito speaks with police after an argument with boyfriend Brian Laundrie
In bodycam images from August 2021, Gabrielle Petito speaks with police after an argument with boyfriend Brian Laundrie Moab City Police Department / Handout

But her family filed a missing person report on September 11 after Petito mysteriously vanished, and Laundrie returned home to Florida without her.

Laundrie refused to say what happened to his girlfriend and then vanished himself, as authorities launched a nationwide search for Petito.

Petito's body was found in the wilderness of Wyoming on September 19, and investigators determined that she had been strangled.

Her death and the subsequent disappearance of the chief suspect sparked a blizzard of media coverage both in the United States and around the world.

Law enforcement agencies during the search of the T. Mabry Carlton Jr. Memorial Reserve for Brian Laundrie
Law enforcement agencies during the search of the T. Mabry Carlton Jr. Memorial Reserve for Brian Laundrie GETTY IMAGES NORTH AMERICA / Octavio JONES

It also triggered debate over the disproportionate attention accorded to missing white women.

Police searched for Laundrie for weeks, until they discovered human remains and "items of interest" in Florida's Carlton Reserve on Wednesday, which were on Thursday confirmed to be Laundrie's.

Brian Laundrie
Brian Laundrie in an image from a police bodycam released by the Moab City Police Department in Utah. Moab City Police Department / Handout

The FBI gave no information on the cause of Laundrie's death.

Investigators said they found a backpack and notebook with the body in a swampy area of the reserve, which is home to alligators, snakes, coyotes and other wildlife.

Laundrie family lawyer Steven Bertolino said in a statement: "Chris and Roberta Laundrie have been informed that the remains found yesterday in the reserve are indeed Brian's.

"We have no further comment at this time and we ask that you respect the Laundries' privacy."

When the body was found on Wednesday, FBI special agent Michael McPherson said an evidence response team would be on scene for several days gathering information.

On their trip, the young couple had shared images online of themselves smiling for the camera, barefoot in a canyon and surveying ochre rocks of state and national parks.

But, after Petito's disappearance, police in Utah revealed one disturbing incident -- a domestic violence report in August.

Police bodycam footage shows a distraught Petito saying she had had an altercation with Laundrie.

Speaking to an officer after their van was pulled over, she is seen crying and saying she struggles with mental health problems.

Petito said she slapped Laundrie after an argument, but she meant no harm.

The police officer decided no charges would be brought but ordered the couple to spend a night apart to calm down.

Weeks of extensive online and media coverage of the case led to renewed debate about so-called "missing white woman syndrome" with appeals for the search effort to find Petito to be matched for other missing people.