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NORTH PORT, Fla. (WFLA) — After several quiet days at the Carlton Reserve – the area that’s been at the center of the search for Brian Laundrie – activity was spotted at one of the entrances on Thursday.

WFLA’s Allyson Henning saw several law enforcement vehicles on the Venice end of the reserve around 9:30 a.m. It was the first time this week our crews have seen activity at the entrance.

Photojournalist Paul Lamison saw several teams moving through the massive nature reserve later as he flew over the scene in Eagle 8 HD.

Two units from the Pasco County Sheriff’s Office were among the law enforcement units seen at the reserve. The public information manager for the sheriff’s office confirmed two K9 units – a human remains detection, or HRD, unit and a K9 trainer – were on scene to help the North Port Police Department, the Sarasota County Sheriff’s Office and the FBI. It was not the first time they’ve been called to assist, their spokesperson said.

“We have sent the HRD K9s a few times and patrol K9s (who are also trained to track those who are missing) a few times,” she said. “For more insight, we’re one of the only law enforcement agencies in Florida that have HRD K9s in house, so we’re often requested to assist in that aspect across the state.”

8 On Your Side reached out to the FBI to confirm that the Pasco Sheriff’s Office units were at the Carlton Reserve to help with the Laundrie search. A spokesperson replied, “as this is an ongoing investigation, there is no additional comment at this time.”

Wednesday officially marked one month since Laundrie’s parents said they last saw him. Laundrie was reported missing by his family on Friday, Sept. 17. At the time, they told police they had last seen him leave home to go to the Carlton Reserve area for a hike on Tuesday, Sept. 14. The family’s attorney, Steve Bertolino, later said that, after further communication with the FBI, the Laundries now believe their son left home to go hiking on Sept. 13.

The day before he was reported missing, Laundrie was named a person of interest in the disappearance of Gabby Petito. The couple had been on a months-long cross-country road trip together before Laundrie returned home to North Port without her on Sept. 1, according to police.

Petito was reported missing on Sept. 11. Her body was found in Wyoming on Sept. 19 and, two days later, her death was ruled a homicide.

The Teton County coroner announced this week Petito’s cause of death was manual strangulation or throttling.

“Manual strangulation or throttling is strangulation by use of hands as opposed to mechanical strangulation,” Dr. Brent Blue told 8 On Your Side’s Mahsa Saeidi.

The coroner’s finding determined she was likely dead for three to four weeks before her body was found.

Laundrie remains the lone person of interest in the Petito investigation. A federal arrest warrant was issued for Laundrie last month for “use of unauthorized access devices” – a Capital One Bank debit card and a personal ID number for two Capital One Bank accounts – following Petito’s death.