A source close to the family of Brian Laundrie told CNN's Chris Cuomo on Thursday that Gabby Petito's fiancé, who is now the subject of a federal warrant, left his parents' Florida home last Tuesday without his cell phone and wallet.
Mr Laundrie's parents were concerned that he might hurt himself, the source said. Mr Laundrie has not been seen since that Tuesday and authorities have been searching a nature reserve in Venice, not far from the parents' home in North Port.
A North Port Police spokesperson declined to comment on the report.
"I can not give any statement to a timeline at this time. That investigation is being conducted by the FBI," North Port Police Public Information Officer Josh Taylor told CNN.
The FBI did not immediately respond to a request for comment.
Earlier, the US District Court of Wyoming issued a federal arrest warrant for Mr Laundrie, according to the FBI's Denver field office, after a grand jury indicted him for his "use of unauthorised devices" after Ms Petito died.
"While this arrest warrant allows law enforcement to arrest Mr Laundrie, the FBI and our partners across the country continue to investigate the facts and circumstances of Ms. Petito's homicide," FBI Special Agent in Charge Michael Schneider said in a statement posted on Twitter.
According to the indictment, Mr Laundrie used a debit card and PIN number for accounts that did not belong to him for charges over US$1,000 between the dates of August 30 and September 1.
The news comes as investigators again searched a 25,000-acre Florida nature reserve for any sign of Laundrie, who returned home September 1 from a road trip without Petito.
Laundrie's family told police he left home with his backpack September 14 and told them he was going to the reserve near their home. On Thursday evening, North Port Police announced via a tweet that it had halted its search for Laundrie at the reserve and that search teams would be back on Friday.
Petito's remains were found Sunday in an undeveloped camping area in Bridger-Teton National Forest in Wyoming, and her death was ruled a homicide on Tuesday in preliminary findings. She was reported missing by her family on September 11.
"We urge individuals with knowledge of Mr. Laundrie's role in this matter or his current whereabouts to contact the FBI," Mr Schneider said Thursday. "No piece of information is too small or inconsequential to support our efforts in this investigation.
An attorney for Laundrie's family emphasised in a statement that the warrant was not for Petito's death but related to activities that took place afterward.
"It is my understanding that the arrest warrant for Brian Laundrie is related to activities occurring after the death of Gabby Petito and not related to her actual demise," Steve Bertolino said.
"The FBI is focusing on locating Brian and when that occurs the specifics of the charges covered under the indictment will be addressed in the proper forum."