What was found
(CAN) COCKPIT, SMELLED LIKE ELECTRICAL FIRE, IN CHARGE DID EMERGENCY CALL REPORTING SMOKE IN CABIN. SOURCE COULD NOT BE IDENTIFIED. RETURNED TO LAND ASAP. WE NOTICED "PACK 1 FAIL" MESSAGE ONCE LANDED ON 06L. IAW AMM 05-50-27 AND DVDR INFO, NO FURTHER ACTION NECESSARY REGARDING OVERWEIGHT LANDING. NR 1 ACM SEIZED, UPON REMOVAL FOUND COMPRESSOR BLADE MISSING AND SEVERE DAMAGE, IDENTIFIED AS CAUSE OF SMOKE, ACM REPLACED IAW AMM 21-51-05-400-801-A. CHECKS SERVICABLE.