TAMPA — The University of South Florida Police Department filed missing persons reports on April 17 for two doctoral students who were last seen that morning in Tampa. The students, Zamil Limon and Nahida S. Bristy, are both 27 years old.

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

Limon was last seen Thursday at 9 a.m. at his Tampa residence, police said. Bristy was last seen Thursday at 10 a.m. in the Natural and Environmental Sciences Building on the USF Tampa campus. Limon's residence is less than a 10-minute drive from that building.

Just before 5 p.m. on April 17, a family friend reported being unable to contact either student. The call prompted police to file missing persons reports for both students and enter them into missing persons databases.

The Hillsborough County Sheriff's Office processed the missing persons report for Limon, and the USF Police Department processed the report for Bristy. Authorities have had no contact with Limon since he was last seen, police said.

Officials said the two students are friends and may be together. Both students were entered into missing persons databases after the family friend's report prompted police to act on April 17.

Police asked anyone who has seen Limon or Bristy or has information regarding their whereabouts to contact the USF Police Department at (813) 974-2628. The department said it will release more information about the case as it becomes available.