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The remains of 23-year-old Brian Laundrie, the man identified as a person of interest in the death of his fiancee, 22-year-old Gabrielle “Gabby” Petito, have been sent to an anthropologist to determine his cause and manner of death, according to multiple reports.

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Steven Bertolino, an attorney representing Laundrie’s family, told WFLA that medical examiners were unable to determine Laundrie’s cause of death after authorities discovered his remains in the Carlton Reserve and the adjacent Myakkahatchee Creek Environmental Park in Sarasota County, Florida.

In a statement, officials with the FBI’s Denver office said that a comparison Thursday of dental records confirmed that remains found one day earlier in an area that had previously been underwater were those of Laundrie. Citing FBI officials, CNN reported that only skeletal remains were recovered.

>> Related: Gabby Petito: FBI confirms remains found in Florida preserve are Brian Laundrie’s

“Everyone knows that … the port was filled with wild animals … alligators and snakes and other animals,” Bertolino told WFTX-TV. “Maybe he drowned. I don’t know. So just the fact that there is skeletal remains, if that’s all there were, doesn’t really tell us much.”

Michael McPherson, the FBI special agent in charge of the agency’s Tampa field office, said Wednesday that officials also found Laundrie’s “personal items,” including a backpack and a notebook.

>> Related: Gabby Petito: FBI finds backpack, notebook belonging to Brian Laundrie in reserve

Authorities had been searching for Laundrie since last month, when his parents reported him missing amid the search for Petito. Police said he was reported missing on Sept. 17, three days after his family said he left for a hike in the Carlton Reserve, though Bertolino told CNN last week that the family notified the FBI of his disappearance on the night he left.

Petito vanished in August during a cross-country road trip with Laundrie. Her remains were found last month in a remote part of Wyoming’s Bridger-Teton National Forest. A medical examiner later determined that she died of manual strangulation.

>> Related: Coroner: Gabby Petito died of strangulation

After the discovery, federal authorities in Wyoming issued a warrant for Laundrie’s arrest, accusing him of using Petito’s debit card “on or about Aug. 30″ through Sept. 1. He was not charged with any other crimes related to Petito’s death.