What was found
LT ENGINE HAD AUTO IGNITION EVENT DURING CRUISE IN CLOUDS WITH ANTI-ICE SYSTEM ON. NO VISIBLE ICE NOTED BY CREW HOWEVER THERE WAS ICE FORCAST. CREW REPORTED 1 IGNITION RELIT AND CONFIRMED IGNITION LIGHTS ON. ALL OTHER PARAMETERS NORMAL. CREW ELECTED TO RETURN TO ANC WHERE MAINTENANCE BORESCOPED COMPRESSOR AND CHECKED ENGINE ANTI-ICE SYSTEM. EVERYTHING WAS FOUND NORMAL AND AIRCRAFT RELEASED FOR SERVICE. NO OTHER PROBLEMS NOTED ON LATER FLIGHTS.