As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW DECLARED AN EMERGENCY AND RETURNED TO GATE DUE TO SMOKE IN THE CABIN ALONG WITH PACK 1 FAIL MSG ON EICAS AT MKE. MAINTENANCE TROUBLESHOT AND FOUND THE PACK 1 ACM TO BE AT FAULT, AND PLACED PACK 1 ON MEL. A/C WAS RETURNED TO SERVICE.