Alex Band Attack -- Cops Scouring Surveillance Footage

Cops in Lapeer, Michigan have already collected surveillance footage from the area where "The Calling" singer Alex Band was allegedly attacked this week ... and are combing through the video looking for an image of the abductors, TMZ has learned.

Law enforcement tells us ... the police BELIEVE Alex's story -- and are treating the situation as an abduction and robbery.

TMZ broke the story ... Alex claims he was snatched off the street around 3AM Sunday morning by unknown assailants who beat the crap out of him before dumping him on some train tracks.

Law enforcement sources tell us ... investigators are planning to release a description of the suspects later today.

Stay tuned ...