North Port, Florida - As the case of Gabby Petito is still shrouded in mystery, her boyfriend Brian Laundrie is still on the run – with time and environmental conditions in South Florida becoming important factors in finding the suspect and solving the case.

The pursuit of Brian Laundrie continues to drag on, without authorities being able to discover any significant leads.

A warrant was issued for Laundrie's arrest on September 23 on fraud charges for unauthorized use of a bank card and withdrawing about $1,000 between August 30 and September 1.

Experts say time is of the essence now in the search for the avid outdoorsman, as the climate in South Florida makes it very difficult to secure forensic evidence, CNN reported.

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The body of his missing girlfriend Gabby was found in Wyoming after he returned home solo from their cross-country camping trip, and her death has been ruled a homicide.

Brian was reported missing by his parents on September 17, after they last saw him three days earlier. He apparently left his parents' home in North Port without his cellphone and wallet, according to a source close to the family.

Images from a surveillance camera allegedly show Laundrie buying a new phone at an AT&T store on the day he disappeared, accompanied by an elderly woman, according to RTL.

He is believed to be somewhere in the depths of the Carlton Nature Reserve in Florida.

It is assumed Laundrie is using the "burner phone" for his needs, which makes his movements hard to track. Some also suspect that his mother may also own one to communicate with her son.

Without new evidence, the search for the 23-year-old is proving difficult.

"Unlike other fugitives or people that are missing, we typically have reason to believe they're in a populated area," said Bryanna Fox, a former FBI agent and criminology professor at the University of South Florida.

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"In this case, it looks like he attempted to maybe go off the grid and is not living in society. So it makes it even harder to find him."

The more time that passes, the less evidence there will be, as the tropical climate is "the hardest on forensic evidence," Fox added.

"Down in Florida, during the summer and wet time, a body can start to skeletonize in less than five to seven days," said Chris Boyer, a spokesperson for the National Association for Search and Rescue. "And with predators, you can lose a lot of evidence that way."

Even though he got a three-day head start over officials, there is still hope of tracking Laundrie down.

"He has to be perfect and make zero mistakes," Fox explained. "Law enforcement, to be able to find him, they either have to find one clue or catch one mistake he made and that could blow the whole case open."

Gabby Petito's death had caused an international stir and sparked a wave of amateur investigations on the internet. That attention has pros and cons.

"The public has to be patient," Fox said.

Gabby's family spoke to the media last week after a large vigil and memorial was held in her hometown.

The search for Brian continues, and speculation remains about whether he is still alive. It's unclear whether authorities can prove his involvement in his fiancé's death – but first, he must be found.