What was found
ABOUT 12 MINUTES AFTER TAKEOFF AND DURING LEVEL-OFF AT 6,000 FEET WHILE ACCELERATING THROUGH 240 KIAS WITH GEAR SELECTED UP AND FULLY RETRACTED, A BIG THUMP WAS HEARD AND THE GEAR UNSAFE LIGHT ILLUMINATED. IT SEEMS THAT THE LEFT MAIN GEAR CAME LOOSE INFLIGHT. WE PROCEEDED TO RUN THE APPROPRIATE CHECKLIST AND LANDED SAFELY IN MMSD. - TECHNICIANS NOTED THE UPLOCK WAS CRACKED.