What was found
CLIMBING THROUGH FL270, A LOUD BANG IN REAR OF ACFT. LT ENGINE COMPUTER LIGHT ILLUMINATED. PF BROUGHT LT ENGINE TO IDLE, PNF PULLED CHECKLIST. AFTER SURVEY OF ENGINE PARAMETERS, PF TURNED LT ENGINE COMPUTER BACK ON TO CONTROL PARAMETERS. ENGINE COMPUTER DID STAY ON & DID APPEAR TO CONTROLL ENGINE. POWER ADVANCED SLOWLY ON LT ENGINE. AT APPROXIMATELY 70 % N1 ANOTHER LOUD BANG IN REAR & LT ENGINE COMPUTER LIGHT ILLUMINATED AGAIN. ENGINE PARAMETERS MOVED TO RED LINE. PF SHUTDOWN LT ENGINE. PNF CONTACTED ATC, DECLARED AN EMERGENCY & REQUESTED & RECEIVED DIRECT CLOSEST AIRPORT. SINGLE ENGINE APPROACH CHECKLIST & PROGRAMMED FMS FOR AN APPROACH. ACFT CLEARED FOR VISUAL APPROACH. AFTER A NON-EVENTFUL LANDING. PAX DEPLANED & ACFT SURVEYED FOR DAMAGE, NONE FOUND. AFTER ENGINE REMOVED & TORN DOWN, DETERMINED A 2ND STAGE LOW PRESSURE COMPRESSOR ROTOR DISC POST SEPARATION. LP SECTION SEIZED.