Brian Laundrie's father, Christopher Laundrie, was seen smiling as he joined the FBI-led search for his missing son at Carlton Reserve in Florida on Thursday. Brian is the prime suspect in Gabby Petito's death.  

According to Daily Mail report, Christopher arrived before 10 a.m. at the 24,565-acre Carlton Reserve in Venice, where authorities believed Gabby Petito's fiance could be hiding. Authorities have been on the hunt for Brian since September 14.

The 62-year-old father of Brian Laundrie joined police officers and park rangers, along with the FBI, in searching the wooded area. Christopher Laundrie was pictured with a young officer who reportedly resembled Brian. The two appeared to be sharing a laugh as they walked along a trail.

Christopher Laundrie reportedly spent hours at the park with about five FBI officers. Investigators invited him to point out his son's favorite trails or spots in the preserve. However, after spending hours at the reserve with "no discoveries," Brian Laundrie's father returned home in the afternoon.

Steve Bertolino, the Laundrie family attorney, said there were no discoveries, "but the effort was helpful to all."

"The entire Laundrie family is grateful for the hard work of the dedicated members of law enforcement that have been searching the Preserve for Brian over the last few weeks. Hopefully, Brian will be located soon," the lawyer noted.

Bertolino said the Laundrie family would continue to cooperate with law enforcement.

On Wednesday, a source close to the Laundrie family told CNN's Chris Cuomo that police had found "remnants" of a makeshift camp at the Carlton Reserve that appeared to have been recently used.

But on Thursday, North Port Police spokesperson Josh Taylor said that no campsite was found, Crime Online reported. The FBI, the lead investigating agency in Brian Laundrie's manhunt, has never confirmed the finding.

READ NEXT: Brian Laundrie Search: Florida Fugitive's Dad Will Join the Search in Carlton Reserve 

Search for Brian Laundrie

Experts in missing persons' cases claimed that Gabby Petito's fiance is likely to have fled the state and may have had help.

Former FBI agent Bryanna Fox, an associate professor of criminology at the University of South Florida in Tampa, said it seems unlikely that he was still in that reserve, NBC News reported.

She added that she believed that Brian Laundrie could no longer be at Carlton Reserve since authorities did not find any trace of him despite weeks of looking for him.

The former FBI agent said that Gabby Petito's fiance may have had financial or transportation assistance to elude authorities. She noted that if someone picked him up hitchhiking or if he boarded a bus, witnesses would likely have gone to the police or the media.

Fox said that the person helping Brian Laundrie would have to be very loyal and close to the fugitive. According to Fox, the weather of the reserve could easily erase any evidence of Laundrie's presence.

"These factors that are here in Florida, a subtropical environment, are known to degrade evidence," she noted.

Aside from the weather, Fox also cited the massive and extremely dangerous landscape, plus the "snakes, gators, and animals" at the reserve that could make it difficult for authorities to find Brian.

Gabby Petito's Mother Believes Brian Laundrie is No longer at Florida's Park

Gabby Petito's mother on Thursday said that she does not believe Brian Laundrie is at the Florida nature reserve. Nichole Schmidt told Fox News that she thinks Brian is in an area like the Appalachian Trail or a campground where he can live off the land since he had those skills.

Gabby Petito disappeared on a cross-country road trip with Brian. The couple was traveling to Oregon when the YouTuber stopped communicating with her family in Wyoming in late August.

Brian was named a person of interest by North Port police after returning home on September 1 or 10 days before Gabby Petito was reported missing by her family.

On September 19, Petito's body was found at the Spread Creek Dispersed Campground near Grand Teton National Park in Wyoming. The FBI has issued a federal arrest warrant for Brian Laundrie but over debit card fraud.

READ MORE: Brian Laundrie Manhunt: Parents of Gabby Petito's Fiancé Change the Date of Florida Fugitive's Disappearance

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Written by: Mary Webber

WATCH: Chris Laundrie Joins Search for Son Brian Laundrie at Carlton Reserve - From WFLA News Channel 8