Brian Laundrie's notebook has revealed he took responsibility for Gabby Petito's death, according to the FBI. 

In a statement released today, the agency said no one else was involved other than her fiance Laundrie, 23. 

"All logical investigative steps have been concluded in this case," Special Agent in Charge Michael Schneider, from FBI Denver, said in the statement shared to Twitter. 

"The investigation did not identify any other individuals, other than Brian Laundrie, [to be] directly involved in the tragic death of Gabby Petito." 

According to the FBI, written statements were found in Laundrie's notebook – one of the items found near his remains – that revealed he claimed responsibility for Petito's death, WFLA reports. 

"Upon further search of the area, investigators found human remains later confirmed to be Mr Laundrie, along with a backpack, notebook, and a revolver. A review of the notebook revealed written statements by Mr Laundrie claiming responsibility for Ms Petito's death," the statement read. 

The FBI stated its primary focus throughout the investigation was to bring justice to Petito and her family. 

"The public's role in helping us in this endeavour was invaluable as the investigation was covered in the media around the world," it read. 

"On behalf of the FBI, I want to express my deepest appreciation to the public for the thousands of tips that were provided during the investigation, and to our local, state and federal law enforcement partners for their work throughout the investigation." 

Petito's family, who met with the FBI in Tampa yesterday, also released a statement through their lawyer shortly before the police announced its findings. 

It revealed that they had "no doubt" that Laundrie murdered her. 

"We truly appreciate the FBI's diligent and painstaking efforts in this extremely complicated case. The quality and quantity of the facts and information collected by the FBI leave no doubt [that] Brian Laundrie murdered Gabby," the statement said. 

The FBI will now work on closing the investigation and will issue a final statement shortly "in the near future," according to WFLA. 

A missing person case was officially opened on September 11 when Petito's mother reported her disappearance to authorities on Long Island, where she and Laundrie met in high school. 

A search was organised of a remote area within the Grand Teton National Park and the Bridger-Teton National Forest. 

On September 19, 2021, the search team located the remains of Petito at the Spread Creek Dispersed Camping Area near where she and Laundrie had been seen together. 

Petito, 22, was found about three weeks after her last known communication, the FBI said in a statement.