Authorities are asking for the public’s help after two 27-year-old doctoral students from the University of South Florida disappeared under unusual circumstances nearly a week ago.

Zamil Limon and Nahida S. Bristy were both last seen on April 16 in Tampa, about an hour apart. Limon, a Ph.D. candidate in geography, environmental science and policy, was last spotted around 9 a.m. at his apartment near campus. Bristy, who is pursuing a doctorate in chemical engineering, was last seen around 10 a.m. at the university’s Natural and Environmental Sciences Building.

A mutual acquaintance reported them missing the following day, April 17, at approximately 4:50 p.m. after being unable to reach either student. Their disappearances prompted separate missing persons reports and a joint investigation by the University of South Florida Police Department and the Hillsborough County Sheriff’s Office. Both have since been listed in state and national missing persons databases.

Investigators say the two are friends and may be together. Both of their phones are turned off, and officials have not released details about potential digital or financial activity. Authorities have also confirmed the pair are not in immigration custody, addressing concerns raised by family members. USF Public Safety Public Information Officer Larry McKinnon said in a statement: “Everybody internally is obviously very concerned, as we are concerned. It’s not typical of their behavior, they’re graduate students. We don’t have information that there is foul play or suspicious nature at this point.”

Police emphasized that their sudden absence is highly unusual, noting both students are described by loved ones as responsible and dedicated to their studies. Limon had been in the U.S. for about two years and was focused on thesis research involving generative AI and Florida’s wetlands. His younger brother, Zubaer Ahmed, said: “He is a very responsible and punctual person, and that’s why the situation is so unpredictable and unusual to us… like, and very suspicious. We’re in deep pain and [a] devastating situation.” Ahmed also shared that Limon and Bristy had discussed a possible future together, though nothing had been finalized.

With few leads, investigators are now turning to the public. “When we get to this point where we aren’t having success in locating them, then our next best source is the public,” McKinnon said. “That’s where we are at.” Officials continue to urge anyone with information about Limon or Bristy’s whereabouts to contact the University of South Florida Police Department at 813-974-2628, as the search remains ongoing.

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