The woman was dressed in mufti when the immigration officer reportedly assaulted her.
The incident happened on Monday. She was said to be traveling to her hometown, Toungo, when the bus she boarded was stopped at a checkpoint mounted by men of the Immigration Service.
The NIS officer was said to have persisted, leading to an angry exchange of words between him and the woman.
He was alleged to have dragged the policewoman out of the bus and beat her into a coma before other people intervened. The woman was rushed to Nodinga hospital, where she was revived.
The incident almost sparked a riot as youths in the area protested against the molestation of women by security personnel who were accused of preying on ladies in the area.
The Adamawa State Police Public Relations Officer, Othman Abubakar, confirmed the incident but declined to disclose the identity of the female police officer.