Workers searching through the wreckage of a passenger jet that crashed Monday in southern China, killing all 132 people aboard, have found one of the plane’s two black boxes. The discovery could help investigators explain why the Boeing 737-800 dove into a hillside in Guanxi province after plummeting from almost 30,000 feet. Chinese state media said the device found at the crash site, where search efforts have been hampered by torrential rain, had been “heavily damaged.” CNBC said it was not clear which black box had been found: the one used to record flight data or the one that records cockpit communications.