Metrolink services between Manchester city centre, Oldham and Rochdale were suspended after a woman was hit by a tram.
Emergency services were called to a collision between a pedestrian and a tram at Oldham Mumps about 08:10 GMT.
The woman's injuries are not believed to be life threatening, Greater Manchester Police said.
Transport bosses said a full service had resumed between East Didsbury and Rochdale but warned of minor delays.
Update: Due to an ongoing police incident, we have NO services operating between Freehold - Rochdale Town Centre. Services will only operate between East Didsbury - Freehold until further notice.— Manchester Metrolink (@MCRMetrolink) February 20, 2019