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NORTH PORT, Fla. (WFLA) – The FBI entry into Brian Laundrie’s parents’ home Sunday was short, with agents seen leaving with a brown paper bag a few minutes after walking through the front door.

Laundrie remains a person of interest in the homicide investigation into the death of his fiancée Gabby Petito.

Petito’s remains were identified by a coroner last week. The 22-year-old whose body was found in Wyoming about 10 weeks after the couple set out on a July journey to several national parks.

The Laundrie’s attorney Steven Bertolino said the agency requested some of Brian Laundrie’s personal items to help with DNA matching. The New York-based attorney said the Laundries cooperated, but he did not elaborate on what was seized.

The FBI also has not revealed what agents have confiscated.

But according to Tylor Barnhart, a forensic biologist at Florida International University’s renowned National Forensic Science Technology Center, investigators do not need a lot due to testing advancements.

“The process has become so sensitive that they would be able to retrieve a DNA profile from just a small sample,” Barnhart said.

DNA could’ve also been gathered last Monday when the FBI searched the home for several hours and left with boxes of potential evidence. Again, the agency would not comment on what was retrieved after that search.

Gabby Petito’s van, driven by Laundrie who slept in the vehicle for weeks, has also been searched, according to police documents.

The Laundrie’s Ford mustang, another potential DNA source, was towed away from the Laundrie home last week, and then returned a day later.

Several sources in law enforcement offered opinions about why additional DNA samples might be collected more than once.

Retired police detective Peter Massey, a criminology instructor at USF, said one potential reason would be to lock down a DNA connection between a suspect and a crime scene.

“Police want to have a known piece of evidence to start with, something they know is connected to a suspect,” Massey said. “We’ll call it a hub. And from that hub we can extend the spokes out to DNA found in the van, DNA found in the swamp area or wherever law enforcement is going to find it.”

Several experts agreed on the one DNA-related item they would want from someone implicated in a crime.

“I would say a toothbrush,” Barnhart said. “Something that he uses every single day that you’re 100 percent sure has his DNA profile on it.”

Barnhart said razors, hairbrushes, and pillowcases are also on the list of preferred DNA sources.

The manner of death was determined by Petito’s autopsy but the cause has not been released. The Wyoming medical examiner who began the autopsy last week said usually the process takes two to three weeks.