Authorities in the Dominican Republic are turning up the heat on the Iowa man who was the last person to see University of Pittsburgh student Sudiksha Konanki before she went missing — grilling him into the early hours Sunday.

Joshua Riibe, a senior at St. Cloud State University in Minnesota, was interrogated by Dominican Attorney General Yeni Berenice Reynoso and navy Vice Adm. Agustin Morillo Rodriguez until nearly 3 a.m., the Spanish-language outlet Noticias SIN reported.

Both high-ranking officials were spotted leaving the RIU Hotel & Resort in Punta Cana, where Riibe, 22, has been “in custody” since shortly after Konanki went missing on March 6, according to the report.

Meanwhile, Riibe is expected to be questioned again on Monday, Noticias SIN also reported.

Riibe is considered a “person of interest” in Konanki’s disappearance, but has not been accused of wrongdoing or charged.

Authorities have seized his passport so he can’t leave until the investigation is finished. They have also put him under police monitoring, the Dominican government said.

“Joshua Steven Riibe, who has been identified as a ‘person of interest,’ remains in custody and is being interrogated at the National Police’s Gender Violence Unit to gather more information about the incident,” a rep for the Caribbean nation said in an update on Friday.

“As long as authorities consider Joshua Steven Riibe a key element in the investigation, he will remain in custody,” the notice said.

A massive search for Konanki entered its 10th day on Sunday, with hundreds of law enforcement personnel involved, including from the FBI, the US Department of Homeland Security and the Loudoun County Sheriff’s Office from her hometown in Virginia.

Police initially believed that the 20-year-old co-ed drowned in the occasionally dangerous surf, which has already claimed three lives this year. But they later said they have not ruled out foul play.

According to police, Konanki and Riibe, along with her friends, stumbled out onto the beach at the upscale resort shortly after 4 a.m. March 6, but the friends later left the pair alone and returned to the hotel.

Surveillance video from the RUI resort shows the two holding hands and staggering arm-in-arm while taking a selfie on a walkway to the beach in the hours before Konanki disappeared.

Riibe allegedly told investigators that the two went into the water but were caught in the rough surf, and said he pulled Konanki to safety but passed out after swallowing water during the ordeal.

He said he asked Konanki if she was OK before passing out.

“It took me a long time to get her out, it was difficult,” Riibe told officials, according to a transcript obtained by Noticias SIN. “I was a lifeguard in the pool, not in the sea.

“The last time I saw her, I asked if she was OK,” he allegedly said. “I didn’t hear her answer because I started vomiting all the sea water I had swallowed.”

Here is the latest information on missing Pitt student, Sudiksha Konanki:

• University of Pittsburgh student Sudiksha Konanki was on spring break in Punta Cana prior to her disappearance.
• Konanki, from Virginia, and her pals went onto the beach from a disco at the Riu Republica Hotel early in the morning following a power outage.
• She was last seen with Joshua Steven Riibe from Iowa, who was named “a person of interest.”
• Sheriff Mike Chapman of Konanki’s hometown in Loudoun County, Virginia, has previously said it is too early to determine if she had drowned.
• Konanki’s parents asked Dominican Republic officials to declare her dead despite her body not being recovered.
• Riibe was officially cleared of wrongdoing Konanki’s disappearance.

Riibe said he woke up and returned to his room, assuming she had also left.

Police said Konanki’s clothes were found on a chaise lounge on the beach.

Authorities have said they believe Konanki may have drowned in the rough currents at the beach but have not ruled out foul play and continue to question Riibe.