What was found
AFTER TAKEOFF AND TURNING ON COURSE, THE CABIN AND COCKPIT BEGAN FILLING UP WITH SMOKE. AN EMERGENCY WAS DECLARED, AND WE BEGAN A QUICK DISCUSSION BETWEEN OURSELVES AND ATC TO SELECT A DIVERSION AIRPORT. SOME EQUIPMENT WAS SHUTDOWN TO ATTEMPT TO STOP THE INFILTRATION OF SMOKE INTO THE CABIN AND COCKPIT INCLUDING THE CABIN FLOOD LIGHTS, COCKPIT RECIRCULATION FAN, AND APU. SENDING APU OUT FOR REPAIR