New Delhi: The search area was on Thursday expanded for the second black box from a China Eastern Airlines passenger jet that crashed in southern China, state broadcaster CCTV said, the Associated Press reported.


This comes a day after one of the black boxes, believed to be the cockpit voice recorder, was found.


The discovery of one black box, which is a recording device used by the aviation investigators to analyse the events leading to the air mishap, may reveal some critical information regarding the cause of the crash as the experts struggle to understand the reason behind the same.


Civil Aviation Authority of China (CAAC) accident investigation division director Mao Yanfeng said the device is so damaged that investigators were not able to tell whether it is the flight data recorder or the cockpit voice recorder.


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“Aircraft black boxes are generally in bright orange-red so they can be found quickly after a flight accident,” according to state-run media Global Times.


“They are built to withstand explosions, disintegration, high temperature combustion, immersion in water and other damage, and the battery lasts for about 30 days,” the state-run media added.


The searchers, as per reports, have been using hand tools, metal detectors, drones and sniffer dogs to comb the heavily forested and steep slopes.


Earlier on Wednesday, the search and rescue efforts for flight MU5735, which was travelling from Kunming to Guangzhou, were forced to halt due to rain, the national broadcaster China Central Television reported.


The Chinese Eastern Airlines plane with 132 people on board crashed in the southwestern province of Guangxi earlier on Monday.