Authorities are searching for two University of South Florida doctoral students who have been missing for days.

Detectives with the University of South Florida Police Department and the Hillsborough County Sheriff’s Office on Tuesday requested the public’s assistance in finding Zamil Limon and Nahida S. Bristy, both 27 years old.

Zamil Limon and Nahida S. Bristy

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Zamil Limon and Nahida S. Bristy

The two were last seen on April 16. Police said they are friends and are believed to be together.

Limon was last seen at around 9 a.m. that day near his residence in the 13000 block of Avalon Heights Boulevard in Tampa. Bristy was last seen around an hour later at the NES Building on USF’s Tampa campus.

Limon is a doctoral student pursuing a degree in geography, environmental science and policy. Bristy, also a doctoral student, studies chemical engineering.

Missing person reports were filed with the university police and the Hillsborough County Sheriff’s Office.

Anyone with information regarding their whereabouts is asked to contact USF police at 813-974-2628.