What was found
FLT 4094 / DTW / TVC- CREW REPORTED VISUALLY AND SMELL SMOKE IN THE CABIN. THEY PULLED INTO THE GATE AND ONLY THE APU WAS RUNNING WITH PACKS ON AT THE TIME WHEN THE SMOKE WAS REPORTED. CREW SHUT THE APU DOWN, DEPLANED, AND CALLED FIRE DEPARTMENT. CONTACTING MAINTENANCE AT THIS TIME. EMERGENCY DECLARED AND EVERYONE IS OK. MAINTENANCE IS EN ROUTE TO COMPLY WITH SMOKE IN THE CABIN WORKSCOPE