As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR RETURN TO DEPARTURE DUE TO LAV SMOKE EICAS WARNING. INFLIGHT, REPORTED SMOKE DETECTED IN BOTH LAV "CHIRPED" WENT INTO ALARM. PERFORMED FIM TASK 21-20-00-810-803-A. NO ODOR WHEN RUNNING PACK NR 1. NR 2 PACK DOES HAVE ODOR. OPENED PACK BAY NR 2 INSPECTED NR 2 ACM AND COOLER AND FOUND COFFEE RESIDUE. REPLACED NR 2 ACM, HEAT EXCHANGER AND FAN BYPASS CHECK VALVE IAW AMM 21-51-05 AND 21-51-04. OPS CHECK GOOD.