Police Capt. Jeff Baker identified the man as Felix Nchikwo (neh-CHIK'-woh).
Baker didn't release Nchikwo's place of residence or school in Canada or his Nigerian hometown.
Authorities say he told a trainer he wasn't feeling well after losing the fight Saturday night at a Port Huron American Legion Post.
Authorities conducted an autopsy Sunday but say it was inconclusive, and they're now awaiting the results of forensic tests to seek the cause of death.
Michigan legislators have been considering regulations for mixed martial arts, including testing fighters for HIV and hepatitis and making promoters cover some medical costs for injured competitors.