Brian Laundrie's family lawyer has been forced to hose down a chilling theory that Laundrie's parents, Roberta and Chris, planted his possessions in Carlton Reserve before they were found by police. 

Steven Bertolino gave his first interview after remains, a backpack and notebook were found in the search for Laundrie, who has been named a "person of interest" in the homicide of his 22-year-old girlfriend Gabby Petito. 

Petito's body was found near a campground in Wyoming on September 19, and within a week her "manner of death" was deemed as homicide by local county coroner Dr Brent Blue. 

In the weeks after Petito was found, and while an active search for Laundrie continued in the dense reserve in Florida, Dr Blue said the final autopsy results identified the cause of death was by strangulation. 

On Wednesday local time, FBI and local law enforcement made the grim discovery of remains in Carlton Reserve — where the search for Laundrie had entered its fifth week. 

Along with the "partial remains", a notebook, backpack and apparent "white dry bag" were found nearby — all likely belonging to the 23-year-old. 

Chris Laundrie's lawyer claims he found a dry bag off the trail. 

Bertolino made the bombshell announcement that Laundrie's father, Chris, found his son's items first, making the discovery in less than 30 minutes inside the nature reserve. 

It is understood police found the backpack, notebook and remains. 

"That area was under water and you can certainly understand why you may not have been able to locate it until today," Bertolino explained to CNN host Chris Cuomo. 

"If water had cleared two weeks ago perhaps they [police]) could have circled back to search again. Perhaps they meant to … but never got back to this part because it is so near to the entrance. 

"Chris and Roberta went to this area first … and they stumbled upon these items." 

Cuomo questioned whether it was unusual that the first day both Chris and Roberta had been on the search site, such a momentous discovery was made — despite dogs and search personnel combing the area previously. 

Chris Laundrie speaks with wife Roberta after appearing to find a white dry bag. 

"Some people don't believe how the events laid out today … but Chris and Roberta walked into the preserve, and they were followed closely by two law personnel," Bertolino explained, calling any allegation his client had "planted" the bag that he found as "hogwash". 

"And when I say close … I mean within eyeshot. As they went further in, Chris went off the trail and into the woods. He was zigzagging in different areas … law enforcement was doing the same thing. 

"Roberta Laundrie was walking down the trail … and at some point Chris locates what is called a 'dry bag'. The dry bag is a white bag laying in the woods 20 feet or so off the trail. "According to Chris, it [the bag was in some bramble." 

Bertolino claims his client didn't want to pick the bag up, instead wanting police to see the item on the ground. But when he couldn't locate the search team, he "picked it up … he met shortly with law enforcement and they looked at the contents of the bag." 

Law enforcement officers drive swamp buggies down a dirt track on the Southside of the Carlton Reserve, as they search for any signs of Brian Laundrie. (Photo / AP) 

"At that point, law enforcement showed him [Chris] a picture on the phone of a backpack that law enforcement had located also nearby," Bertolino explained. 

"At that point the Laundrie's were notified that there was also remains near the backpack … and they were asked to leave the preserve." 

Bertolino said upon hearing that remains had been discovered, his clients were "heartbroken". 

"It's quite sad … you can imagine as a parent finding out your son's belongings alongside remains … that has got to be heartbreaking," he said. "I can tell you they are heartbroken." 

"The probability is strong that it is Brian's remains but we are going to wait for the forensic results to come in to verify that." 

An autopsy has yet to be released to confirm if the remains are in fact Brian Laundrie. FBI officials say personnel will be on site for days combing for any further evidence. 

By Vanessa Brown, news.com.au