According to the police, they had appeared in the departmental recruitment examination held at the CRPF campus at 9th Mile.
The four youths sat for the Citi GD physical examination on behalf of others through PST/PET of the CRPF, officials said.
Meanwhile, the assistant commander at the CRPF 9th Mile camp, Amosh Lana had lodged a complaint at the Jorabat police station, based on which police had initiated investigation into the matter.
The detained youths have been identified as Subnar Basumatary, Lauga Brahma, Samjit Narzary and Bilar Basumatary.
On the other hand, allegations over other such cases of people appearing on behalf of actual candidates in the written stage of the examination have come up.
Officials informed that they will continue the investigations in the matter.