NORTH PORT, Fla. — Authorities are searching a vast area of rural Sarasota County Sunday for Brian Laundrie, a person of interest in the disappearance of his girlfriend, Gabby Petito.

Petito was last seen on Aug. 30 in the area of Grand Teton National Park, investigators say. 

Laundrie, 23, and Petito, 22, left in July on a cross-country trek in a converted van to visit national parks in the U.S. West. Police said Laundrie was alone when he drove the van back to his parents’ home in North Port, on Sept. 1. 

Petito’s family reported her missing 10 days later on Sept. 11.

Laundrie is now also missing — his family said the last time the saw him was Tuesday before he went for a hike in the Carlton Reserve.

More than 50 North Port police officers, FBI agents and members of other law enforcement agencies are again searching in the 24,000-acre reserve Sunday.

Investigators have been searching for Laundrie at the Carlton Reserve area of Sarasota County since early Saturday, but have so far not found any trace of him.

Authorities used drones, scent-sniffing dogs and all-terrain vehicles in the reserve, which has more than 100 miles of trails, as well as campgrounds. Investigators took some of his clothing from his parents’ home Friday night to provide a scent for the search dogs.

“His family says they believe he entered the area earlier this week,” North Port Police tweeted Saturday.

Meanwhile, the FBI in Denver said Saturday that agents were conducting ground surveys at Grand Teton National Park in Wyoming, with help from the National Park Service and local law enforcement agencies, seeking clues to Petito’s disappearance. Her last known contact with family members was from the national park known for its mountainous terrain.

Investigators in Florida were hopeful Laundrie was somewhere in the wildlife reserve near Sarasota. Depending on his skills, he could survive out in the reserve for some time, said police spokesperson Josh Taylor at a news conference.

“Certainly, we prepare for all different possibilities, but you know, our goal is to locate him and bring him back to North Port,” Taylor said.

Police said the conversation Friday evening was the first time they'd spoken with the Laundries in detail about the case, and that the meeting came at the family's request. An attorney for the family called FBI investigators and said they wanted to talk about Laundrie's disappearance, police said.

Anyone with information is asked to call 1-800-CALL-FBI.

Attorneys for the Petito family released a statement saying that Laundrie was not “missing.”

“All of Gabby's family want the world to know that Brian is not missing, he is hiding. Gabby is missing,” the statement from the law office of Richard B. Stafford said.

The Associated Press contributed to this report.