Human remains were found in a thickly wooded Florida park on Wednesday, near a notebook and other items belonging to a man who has been declared a “person of interest” in the murder of his fiancée, the F.B.I. said.
The discovery came seven weeks after the man, Brian Laundrie, returned home from a monthslong van trip without the fiancée, Gabrielle Petito, and about four weeks after she was found dead in a national forest in Wyoming.
Michael F. McPherson, the special agent in charge of the F.B.I.’s Tampa field office, said that the authorities had found a notebook and a backpack that belonged to Mr. Laundrie, near what appeared to be human remains in the Myakkahatchee Creek Environmental Park, a heavily wooded, 160-acre park in North Port, Fla.
The park connects to the Carlton Reserve, a 24,565-acre wildlife refuge, where the authorities had been searching for Mr. Laundrie for weeks. The items were found in an area that until recently had been underwater, Mr. McPherson said.
He said that an evidence response team was using “all available forensic resources” to process the scene, which could take several days. The reserve and the park have been closed to the public, he said.
“I know you have a lot of questions, but we don’t have all the answers yet,” Mr. McPherson said at a news conference at which he did not take questions. “We are working diligently to get those answers for you.”
The discovery of the remains could end the search for Mr. Laundrie after Ms. Petito’s body was found in September in the Bridger-Teton National Forest, by Grand Teton National Park in Wyoming.
A coroner determined that the manner of Ms. Petito’s death was homicide, and that the cause was strangulation. The coroner, Dr. Brent Blue of Teton County, Wyo., said her body had been outside for three to four weeks before it was found on Sept. 19.
Mr. Laundrie’s items and the remains were found on Wednesday after his parents, Chris and Roberta Laundrie, had informed the F.B.I. and the police on Tuesday evening that they intended to come to the park on Wednesday morning to search for their son, the family’s lawyer, Steven Bertolino, said in a statement. Mr. Bertolino said that law enforcement officials had met the parents at the park on Wednesday morning.
After a brief search off a trail that Mr. Laundrie frequented, the family and law enforcement officials found “some articles” belonging to him, Mr. Bertolino said. The discovery prompted a “more thorough investigation of that area” by law enforcement agencies.
The Pasco County Sheriff’s Office confirmed on Wednesday that it had brought a dog specially trained to find human remains to the park, at the request of the local police.
The authorities and Ms. Petito’s family members were still grasping for answers about what happened during and after the couple’s cross-country road trip, which Ms. Petito, 22, and Mr. Laundrie, 23, chronicled at length on social media.
Ms. Petito left with Mr. Laundrie from New York in July in a white Ford van outfitted with a bed and other necessities for visiting national parks and nomadic travels that they called “Van Life.”
On Sept. 1, Mr. Laundrie returned to the home in North Port, Fla., where he and Ms. Petito had been living. He drove there, alone, in the van, which had been registered to Ms. Petito.
Ten days later, Ms. Petito’s family reported her missing. The search for her soon involved the F.B.I. and National Park rangers and stretched across at least two states. Through a lawyer, Mr. Laundrie had declined to speak to investigators, according to the police, who described him as a “person of interest” and not as a suspect.
Then, six days after Ms. Petito was reported missing, Mr. Laundrie’s parents told the police that they had not seen him for several days, starting a second search for a missing person. The authorities began to scour the Carlton Reserve, and the F.B.I. served a search warrant at the Laundrie residence.
On Aug. 12, the police in Moab, Utah, responded to a report of a “domestic problem” between the couple, according to a police report. It said that Mr. Laundrie and Ms. Petito had “some sort of argument.”
The report said that he told her to take a walk and calm down, and that Mr. Laundrie and Ms. Petito both told the officers that they were in love, engaged to be married and “desperately didn’t wish to see anyone charged with a crime,” the report said.
Mr. Laundrie told one officer that “issues between the two had been building over the last few days,” it said.
Body camera footage shows that, during the encounter, Ms. Petito cried and said she suffered from anxiety. In the police report, Ms. Petito is recorded as saying she moved to slap Mr. Laundrie because she feared that he “was going to leave her in Moab without a ride.”
Both told the police that the episode should be classified as a “mental/emotional health ‘break’” and not as domestic assault, the report said.
The police described Mr. Laundrie in the report as the victim of the incident. They arranged for him to stay in a hotel that night while Ms. Petito kept the van. No charges were filed, the report said.
Alan Yuhas contributed reporting.