Man seen with missing Pitt student believes he's being detained illegally: Source

PUNTA CANA, Dominican Republic -- Lawyers for the Minnesota college student who was with University of Pittsburgh student Sudiksha Konanki the night she went missing in Punta Cana have requested a habeas corpus hearing, a source from the Dominican Republic Ministry of Justice told ABC News.

Joshua Riibe -- who has not been charged with a crime -- has been questioned by prosecutors over three days, an official close to the investigation told ABC News.

Riibe's lawyers believe he's being detained illegally and want to prevent the 22-year-old from being placed in custody, the source said. Authorities have confiscated Riibe's passport and his attorneys said he's being surveilled at his hotel.

In the Dominican Republic, people can challenge an unlawful detention through a habeas corpus hearing. Detained individuals are required to be brought before a judge within 48 hours, or they must be either charged or released.

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A ruling on the habeas corpus hearing request cannot prevent an order of arrest by Dominican authorities, according to Riibe's lawyer and a source from the Dominican Republic Ministry of Justice.

Authorities said they believe 20-year-old Konanki died by drowning, officials told ABC News.

Her missing persons case is being treated as an accident, sources said. Authorities said Riibe is not a suspect and is cooperating and being questioned as a witness.

Sources familiar with the investigation say the lead prosecutor is examining possible contradictions in his story.

Officials are also reviewing new surveillance video captured the night before Konanki went missing on March 6 from inside the RIU hotel nightclub, which shows Konanki and Riibe appearing to get sick.

Konanki was on spring break with her friends in Punta Cana when she went missing in the early hours of March 6.

She was part of a group that went to a nightclub and then for a walk on the beach, officials involved in the investigation told ABC News.

Most of the group went back to the hotel around 5:55 a.m. after their night of drinking.

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Riibe -- who Konanki met that night -- stayed with her on the beach, according to a Dominican Republic investigative police report.

Riibe told the prosecutor the two went swimming and kissed. He said then they were hit by a wave and pulled into the ocean by the tide, according to a transcript provided to ABC News from two Dominican Republic sources.

Riibe said he held Konanki and tried to get them out of the water.

"I was trying to make sure that she could breathe the entire time -- that prevented me from breathing the entire time and I took in a lot of water," he said.

"When I finally touched the sand, I put her in front of me. Then she got up to go get her stuff since the ocean had moved us," Riibe told the prosecutor. "She was not out of the water since it was up to her knee. She was walking at an angle in the water."

"The last time I saw her, I asked her if she was OK. I didn't hear her response because I began to vomit with all the water I had swallowed," he said. "After vomiting, I looked around and I didn't see anyone. I thought she had taken her things and left."

Riibe said he passed out on a beach chair and woke up hours later and returned to his hotel room.

Police confirmed two images show her swim coverup and shoes that were recovered on the beach.

Hotel cameras captured him returning to his room that morning.

He is expected to face more questioning on Monday.

The Riibe family issued a statement, saying in part, "We express our deep sorrow and solidarity with the family of Sudiksha Konanski during this painful time. Above all, we wish to contribute to the search efforts and understand the anguish and uncertainty they are going through and we share the hope that Sudiksha will be found as soon as possible."

ABC News' Ellie Kaufman contributed to this report.