ABUJA, Nigeria (AP) — Gunmen attacked a passenger bus in Nigeria ‘s Benue state, abducting some students on their way to university examinations, officials said.

The students and other passengers were abducted Thursday along the Otukpo-Makurdi highway, Benue Gov. Hyacinth Alia said in a statement.

The governor did not specify how many were taken, but local media said 14 passengers were on board.

“The targeting of innocent citizens, particularly students on their way to sit for examinations, is unacceptable and stands against every norm of humanity and civil order,” Alia said.

Search and rescue operations are underway in the central state to ensure the safe return of all abducted persons, the governor said.

No group has claimed responsibility for Thursday’s abductions. Benue has been a hot spot for armed violence in a region where armed gangs often target remote villagers and travelers with violent killings and kidnapping for ransom.

Students’ kidnappings have come to define the insecurity in Africa’s most populous nation, and analysts say it’s often because armed gangs see schools and students as “strategic” targets to draw more attention.

Alia urged residents to remain calm and to continue to cooperate with security agencies on rescue efforts and other operations.

“We will continue to take decisive actions to protect lives and property,” he added.