As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK DUE TO NR 1 BLEED DUCT LEAK EICAS MESSAGE WITH ASSOCIATED DUCT LEAK LIGHT. PERFORMED WING LEAK BODY DUCT LEAK DETECT. FOUND BODY CROSSOVER DUCT IN AFT AIR CON BAY LEAKING IAW AMM REF AMM 36-11-01-404-142-001 TIGHTENED CLAMP AFTER REPOSITIONING SLEEVE. OPS AND LEAK CK GOOD.