Tuesday marks 12 days since Sudiksha Konanki, a University of Pittsburgh student, disappeared while on a spring break trip to the Dominican Republic. The situation has prompted a widespread search from both U.S. and local authorities by land, air and water — but so far she hasn’t been found.

Konanki’s family believes the 20-year-old pre-med student, who was last seen on video surveillance on March 6, drowned in Punta Cana, the Loudoun County Sheriff’s Office in Virginia, where Konanki is from, said in a statement released Tuesday.

“Sudiksha’s family has expressed their belief that she drowned,” said Sheriff Michael Chapman. “While a final decision to make such a declaration rests with authorities in the Dominican Republic, we will support the Konanki family in every way possible as we continue to review the evidence and information made available to us in the course of this investigation.”

It comes after Konanki’s family had sent a letter to Dominican Republic authorities requesting a declaration of her death, NBC News reported, citing a police spokesperson. Her family also sent a similar letter to the Loudoun County Sheriff’s Office “seeking closure” amid the investigation, People reported.

When Konanki was last seen earlier this month, she appeared to enter the beach before dawn with her friends and two other men, according to Dominican Republic National Police.

One of the men, Joshua Riibe, 22, is believed to have been the last person with Konanki on the beach near the Hotel Riu Republica Resort in Punta Cana, where she was staying before she vanished.

Riibe has been questioned by authorities from various agencies about his final moments on the beach with Konanki to examine possible inconsistencies in his story. Last week he was identified as a “person of interest,” the sheriff’s office in Loudoun County said. Authorities also stressed that it is not a criminal case at this time.

Riibe’s passport was confiscated last Friday by Dominican authorities as part of the missing person investigation. The law firm representing Riibe said in an email to NBC News that Riibe “has been confined to the hotel since the investigation began. He is permanently escorted by the police anywhere he goes. So no, he is not free to leave.”

Riibe’s attorneys have filed a habeas corpus petition to have him released. A hearing on the petition will be held on March 18, according to Dominican outlet Noticias SIN.

Meanwhile, newly obtained surveillance footage by the news agency this week purportedly shows Konanki and Riibe hanging out near each other at a bar just hours before her disappearance. The two never interact in the video. The person who appears to be Konanki leans over a grassy area, seemingly to vomit. Riibe is nearby hunched over the grass, as if to also vomit.

The preliminary timeline of Sudiksha Konanki’s disappearance

Missing person posters describe Konanki as 5 feet, 3 inches tall, with black hair and brown eyes. She was last seen wearing a brown bikini, big round earrings, a metal designer anklet on her right leg, yellow and steel bracelets on her right hand and a multicolored beaded bracelet on her left hand.

March 3: Konanki arrived in the Dominican Republic with five friends. They were all staying at the Hotel Riu Republica in Punta Cana.

March 5: Konanki told her friends that she was going to a party at the resort, her father told CNN.

March 6:

• 4:15 a.m. local time: Konanki and her friends were seen on video surveillance footage entering the beach area of the resort, police said.
• Around 6 a.m.: Surveillance cameras captured five women and one man leaving the beach. Konanki is believed to have stayed behind with a young man, CNN reported, citing a local police source.
• 9:55 a.m.: That same police source said the man was leaving the beach, with no apparent sign of Konanki.
• 4 p.m.: Konanki’s friends reported her missing, since it had been 12 hours since she was last seen, the Riu hotel chain said in a statement. The sheriff’s office in Loudoun County, Va., where she and her family live, was notified of Konanki’s disappearance.

March 7: Police in the Dominican Republic learned of her disappearance after 8 a.m. in a call from the U.S. Embassy in Santo Domingo.

The Hotel Riu Republica, where Konanki was a guest, told People that a “red flag was placed on the beach” around the time that she vanished. The resort says the red flag provides a warning that “the sea had a strong current and very high waves.”

Last week, the International Criminal Police Organization (Interpol) issued a yellow notice — a worldwide police alert for a missing person — which will notify authorities if Konanki travels to another country.

Dominican police lead investigation, with help from U.S.

The Loudoun County Sheriff’s Office said in a March 9 statement that it is working closely with authorities from the State Department, FBI, DEA, Homeland Security Investigations and the University of Pittsburgh police “in support of the ongoing investigation by the Dominican National Police.”

Konanki is a citizen of India and a permanent resident of the United States, and the Indian Embassy in the Dominican Republic is helping in the investigation.

The hotel where Konanki is staying is also supporting the search efforts. “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,” the hotel said. “We would like to express our deepest sympathy to the family and friends during this incredibly difficult time. … We are fully committed to doing everything in our power to assist in this situation.”

Surveillance video obtained by Noticias SIN

What the missing person investigation has found so far

Last week, Dominican authorities moved the search from the hotel, where Konanki was staying, to Macao Beach. Officials at the resort say water conditions were potentially dangerous on the day of her disappearance.

There is no information about whether a body has been found, Regional Red Cross Director Fernando Placeres said Sunday.

Loudoun County Sheriff Michael Chapman said authorities are combing through security footage and cellphone data for any sign of Konanki.

“We have certainly experts here within the U.S. that will look into all aspects of her phone, her friends’ phones, anybody that she might have been with, to see exactly what may have happened there,” Chapman said.

The sheriff’s office doesn’t have jurisdiction over the investigation, but sent detectives to help with the U.S. said of the investigation in Punta Cana.

The public prosecutor’s office has also interviewed Konanki’s friends, NBC News reported.