Platinum-selling rapper Fat Joe was detained by police in Madison, Wisconsin last night after a 33 year old woman told cops that Joe and his entourage sexually assaulted her inside a Cadillac limo.

According to the Madison PD, the woman claims the incident went down after the rapper, real name Joseph Cartagena, performed at a concert at The Orpheum Theater last night.

Cops say the woman claims, "shortly after the concert had concluded ... [the woman] found herself inside of a Cadillac Limousine with Joseph Cartagena and other male subjects all with the destination of a hotel located on Madison's west side."

So far, no arrests have been made and police say the investigation is ongoing.