US authorities said a body found in a national forest in Wyoming, where a search was under way for Gabrielle "Gabby" Petito, matches the description of the missing woman.
A massive search was launched for 22-year-old Petito when her family filed a missing-person report on September 11, after she mysteriously vanished during a road trip with her boyfriend.
The cause of death had not been determined, the FBI said on Sunday.
"Earlier today human remains were discovered consistent with the description of Gabrielle 'Gabby' Petito," AFP reported, quoting the FBI.
"Full forensic identification has not been completed to confirm 100 per cent that we found 'Gabby', but her family has been notified of this discovery."
The FBI and other law enforcement had been searching for Petito in a national forest in the western state of Wyoming, where the couple was when Petito last communicated with her parents in late August, according to her family.
Petito quit her job and packed her life into a camper van for a cross-country adventure in July with her boyfriend Brian Laundrie, 23, documenting their journey in a stream of idyllic-seeming Instagram posts.
But more than two weeks ago, Mr Laundrie returned to his home in North Port, Florida, alone in Petito's van. Ten days later, her family filed a missing-person report.
Mr Laundrie was declared a "person of interest" in the case and declined to co-operate with police.
The mystery deepened after Mr Laundrie also went missing.
On Friday, North Port police said Mr Laundrie's parents claimed they had not seen their son for several days.
In a statement, the police underscored that while he was a person of interest, "he is not wanted for a crime".
The couple embarked on their journey across the US from New York on the East Coast, posting photos of magnificent views of the American West and the two of them smiling happily next to their small white van.
In one YouTube video published during their trip, Petito and Laundrie are shown kissing, enjoying a sunset together and strolling on a beach.
However, in August, police in Utah responded to a domestic violence report involving Petito and Mr Laundrie.
Police body-cam footage published by US media shows a distraught Petito saying she had had an altercation with Mr Laundrie.
Speaking to a police officer after their van was pulled over, Petito is seen crying and saying she struggles with mental health problems.
Petito said she slapped Mr Laundrie after an argument, but added that she meant no harm.
"We've just been fighting this morning, some personal issues," she said. "He wouldn't let me in the car before... he told me I needed to calm down."
Mr Laundrie told police that Petito tried to get the van keys from him and he pushed her before she hit him with her phone.
The police officer decided no charges would be brought but ordered the couple to spend a night apart to calm down.
News of Petito's disappearance sparked a flood of calls on social media to help find her.
Her father, Joe Petito, appealed for anyone with information on her whereabouts to contact the authorities, adding that an anonymous tip line had been set up.