The authorities have been searching by land, air and sea for a University of Pittsburgh student who disappeared last week while on spring break in the popular Dominican Republic resort of Punta Cana.
The National Police said in a statement on Sunday that the student, Sudiksha Konanki, 20, was last seen early Thursday when she went to the beach by the Hotel Riu Republica with an unnamed friend who has been “under investigation.”
Ms. Konanki, a resident of Loudoun County, Va., had been staying at the hotel 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.
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 a few meters from the beach entrance, the police said.
Investigators were interviewing the people who were with her to help guide the search, the police said.
Investigators also conducted a preliminary interview with a young man who had been in the water and were trying to corroborate his account, the police said. The statement did not detail what the young man had told investigators.
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.”
WTOP, a Washington-area news station, reported on Monday that Ms. Konanki’s father, Subbarayudu Konanki, had 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.
The complaint stated that Ms. Konanki’s belongings, including her phone and wallet, had been left with her friends, “which is unusual because she always 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. Subbarayudu told the station. “She’s not found, so we’re asking them to investigate multiple options, like kidnapping or abduction.”
The Loudoun County sheriff, Mike Chapman, said he was helping U.S. officials who were working with the Dominican National Police on the search.
He 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.
On Tuesday, Thomas Julia, a spokesman for the Loudoun County Sheriff’s Office, said that the Dominican authorities have been interviewing a number of young people who were on the beach, including two American men.
He said there had been a “red-flag” warning for rough surf on the beach around the time that Ms. Konanki was last seen.
The case was “still being treated as a missing person,” Mr. Julia said in an interview. “It is not being treated as a criminal investigation because there is no evidence of a crime.”
He said that investigators were trying to determine who was last with Ms. Konanki and what may have happened to her. “Nobody can vouch for what exactly happened to her,” Mr. Julia said, adding that some of the people on the beach were intoxicated.
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. It added: “The safety and well-being of our guests are our highest priority, 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 and takes pride in its reputation as a safe place for tourists. “We are one of the safest countries, not just in Latin America, but in the world,” he said.
Hogla Enecia Pérez contributed reporting.