As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO DEPARTURE, LAV SMOKE EICAS WARNING AT 500 AGL CABIN CREW REPORTED SMOKE IN AFT CABIN. ACCOMPLISHED INSPECTION FOR SMOKE IN CABIN. FOUND EVIDENCE OF COFFEE GRINDS IN NR 2 PACK ACM ASSEMBLY. R & R NR 2 ACM IAW MM 21-51-05, NO LEAKS NOTED, OPS CHECKS GOOD ADDITIONAL COMPONENT CHANGE IAW MCC R/R DUAL HEAT EXCHANGER IAW MM 2-51-04. OPS CHECKS GOOD.