The authorities have interviewed a man who may have been the last person to see a University of Pittsburgh student before she disappeared last week while on spring break in the Dominican Republic, an American official said.
The Dominican National Police said in a statement that the student, Sudiksha Konanki, 20, of Loudoun County, Va., was last seen early Thursday when she went to the beach in Punta Cana with an unnamed friend who was “under investigation.”
Chad Quinn, a spokesman for the Loudoun County Sheriff’s Office, said on Wednesday that the man, who may have been the last to see Ms. Konanki, is believed to be an American citizen who was vacationing in Punta Cana, but was not part of the group of friends traveling with Ms. Konanki.
The New York Times is not identifying the man because he has not been charged with a crime.
He is “a person of interest in a missing-person investigation,” Mr. Quinn said in an email. “This is not at this time a criminal investigation. So to be clear, he is not a suspect.”
Mr. Quinn added that the man, who he did not believe was in custody, had spoken to the Dominican authorities “a couple of times.”
Thomas Julia, another spokesman for the Sheriff’s Office, said that some of the people who were on the beach with Ms. Konanki were intoxicated. “Nobody can vouch for what exactly happened to her,” Mr. Julia said.
The Dominican president, Luis Abinader, said at a news conference on Monday that the authorities were carrying out a special operation at sea “because the latest information we have from the last person who was with the young woman — according to reports — is that while they were on the beach, a wave crashed into them and caused some kind of situation.”
“We are investigating to clarify exactly what happened,” Mr. Abinader told reporters, adding, “What is being investigated is an accident, basically.”
Ms. Konanki’s father, Subbarayudu Konanki, traveled to the Dominican Republic and filed a complaint on Sunday, asking the authorities to broaden the investigation beyond the possibility of an accidental drowning, WTOP, a Washington-area news station, reported on Monday.
The complaint stated that Ms. Konanki’s belongings, including her phone and wallet, had been left with her friends, and it called this “unusual” because she typically carried her phone with her, WTOP reported.
“It’s four days, and if she was in water, she would likely have been strewn to shore,” Mr. Konanki told the station. “She’s not found, so we’re asking them to investigate multiple options, like kidnapping or abduction.”
Ms. Konanki had been staying at the Hotel Riu Republica in Punta Cana with five friends after arriving in the Dominican Republic on March 3, the police said.
When the United States Embassy in the Dominican Republic alerted the national police on Friday morning that Ms. Konanki had disappeared, officials began an exhaustive search of the beach and the surrounding area, using drones, helicopters, divers, boats, police dogs and other resources, the authorities said.
More than 300 agents have been searching for Ms. Konanki, and they are re-interviewing some of the people who were with her, the police said on Tuesday. The F.B.I. is helping in the investigation, according to the Loudoun County Sheriff’s Office.
Investigators have established that Ms. Konanki disappeared sometime after 4:15 a.m. on Thursday, when she and other young people she was with were seen on surveillance video near the beach entrance, the police said.
The Loudoun County sheriff, Mike Chapman, told NewsNation that it was “way too premature” to assume that Ms. Konanki had drowned and said that there were “inconsistencies” in some of the accounts given by the young people who had been with Ms. Konanki.
Riu Hotels and Resorts said it was “deeply concerned” about the disappearance of one of its guests.
“From the moment her absence was reported, we have been working closely with the local authorities, including the police and the navy, to conduct a thorough search,” it said in a statement. “The safety and well-being of our guests are our highest priority,” it added, “and we are fully committed to doing everything in our power to assist in this situation.”
The Dominican Republic depends heavily on foreign tourism, and Punta Cana, known for its white sand beaches, golf courses and all-inclusive resorts, is the country’s most popular destination.
About eight million passengers travel through Punta Cana International Airport each year, making it the busiest airport in the Dominican Republic and the second busiest in the Caribbean, according to its website.
Mr. Abinader, the Dominican president, said the country receives more than 11 million visitors per year. “We are one of the safest countries, not just in Latin America, but in the world,” he said.
Ali Watkins and Hogla Enecia Pérez contributed reporting.
