Officials with the Civil Aviation Authority of China said the device was so damaged that they were unsure if it was a flight data recorder or the cockpit voice recorder, The Associated Press reported.
Mao Yanfeng, the accident investigation division director, did not say if the recording device inside the box was damaged.
He said search crews are still trying to find the second black box.
While they are called black boxes, the devices are actually orange so they can be easily seen, the AP reported.
Rain fell on the crash site causing the search to be temporarily halted.
Crews are using hand tools, drones and dogs to look for any human remains. They’re also pumping water out from the pit where the plane hit the ground.
Mao said the crew members were all healthy and had regular contact with air traffic controllers during the flight. The plane had a clean maintenance record and the weather was good during the flight.
Flight MU5735 went into a dive, dropping from a cruising altitude of 29,098 feet to 4,375 feet in a matter of three minutes, CNN reported.
According to FlightRadar24, the plane fell at a rate of 31,000 feet a minute, or about the height of a 50-story building every second, according to Reuters.
Eyewitnesses said they saw a plane falling from the sky.
“The plane fell vertically from the sky. Although I was very far away, I could still see that it was a plane. The plane did not smoke during the fall. The fire started after it fell into the mountain, followed by a lot of smoke,” the witness said, according to CNN.
There were 132 people on board the flight. No survivors have been found, Reuters reported.
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Photos: China Eastern flight carrying 132 people crashes in Guangxi This screen grab taken from video from The Paper and received via AFPTV on March 21, 2022, shows ambulances turning off onto a side road upon arrival after a China Eastern reportedly crashed in Teng County in Wuzhou City, Guangxi province. (STR/AFPTV/AFP via Getty Images)
Photos: China Eastern flight carrying 132 people crashes in Guangxi In this image taken from video footage run by China's CCTV, emergency personnel travel to the site of a plane crash near Wuzhou in southwestern China's Guangxi Zhuang Autonomous Region, Monday, March 21, 2022. (CCTV via AP)
Photos: China Eastern flight carrying 132 people crashes in Guangxi In this image taken from video footage run by China's CCTV, emergency personnel prepare to travel to the site of a plane crash near Wuzhou in southwestern China's Guangxi Zhuang Autonomous Region, Monday, March 21, 2022. (CCTV via AP)
Photos: China Eastern flight carrying 132 people crashes in Guangxi In this image taken from video footage run by China's CCTV, emergency personnel prepare to travel to the site of a plane crash near Wuzhou in southwestern China's Guangxi Zhuang Autonomous Region, Monday, March 21, 2022. (CCTV via AP)
Photos: China Eastern flight carrying 132 people crashes in Guangxi In this image taken from video footage run by China's CCTV, emergency personnel prepare to travel to the site of a plane crash near Wuzhou in southwestern China's Guangxi Zhuang Autonomous Region, Monday, March 21, 2022. (CCTV via AP)
Photos: China Eastern flight carrying 132 people crashes in Guangxi A flight information board shows a cancelled China Eastern Airlines flight (top) at the Kunming Changshui International Airport in China's southwestern Yunnan province on March 21, 2022, after a China Eastern aircraft flying from Kunming to the southern hub of Guangzhou crashed in southwestern China. (STR/AFP via Getty Images)
Photos: China Eastern flight carrying 132 people crashes in Guangxi Passengers sit in front of the self-service machines of China Eastern Airlines in Kunming Changshui International Airport in China's southwestern Yunnan province on March 21, 2022, after a China Eastern aircraft flying from Kunming to the southern hub of Guangzhou crashed in southwestern China. (STR/AFP via Getty Images)
Photos: China Eastern flight carrying 132 people crashes in Guangxi A staff member holds up a board to guide relatives of passengers on China Eastern flight MU5375 after it failed to arrive at Guangzhou Baiyun International Airport in China's southern Guangdong province on March 21, 2022. (STR/AFP via Getty Images)
China Eastern Airlines crash investigation In this image taken from video footage run by China's CCTV, a search and rescue worker holds the second orange-colored "black box" recorder which recovered at the China Eastern flight crash site in Tengxian County on Sunday, March 27, 2022, in southern China's Guangxi Zhuang Autonomous Region. The second "black box" has been recovered from the crash of a China Eastern Boeing 737-800 that killed all 132 people on board last week, Chinese state media said Sunday. (CCTV via AP Video) (AP)
China Eastern Airlines crash investigation In this photo released by Xinhua News Agency, officials and search and rescue workers bow and pause for a three-minute moment of silence for the 132 people killed, at the China Eastern flight crash site in Tengxian County on Sunday, March 27, 2022, in southern China's Guangxi Zhuang Autonomous Region. The second "black box" from a China Eastern Boeing 737-800 was found Sunday, raising hopes that it might shed light on why the passenger plane nosedived into a remote mountainous area in southern China last week, killing all 132 people on board. (Huang Xiaobang/Xinhua via AP) (Huang Xiaobang/AP)
China Eastern Airlines crash investigation CORRECTS NUMBER OF THE VICTIMS - In this photo released by Xinhua News Agency, search and rescuer workers conduct continued search operations at the China Eastern flight crash site in Tengxian County on Saturday, March 26, 2022, in southern China's Guangxi Zhuang Autonomous Region. The second "black box" has been recovered from the crash of a China Eastern Boeing 737-800 that killed 132 people last week, Chinese state media said Sunday. (Lu Boan/Xinhua via AP) (Lu Boan/AP)
China Eastern Airlines crash investigation In this photo released by Xinhua News Agency, search and rescue workers pause for a three-minute moment of silence for the 132 people killed at the China Eastern flight crash site in Tengxian County on Sunday, March 27, 2022, in southern China's Guangxi Zhuang Autonomous Region. The second "black box" from a China Eastern Boeing 737-800 was found Sunday, raising hopes that it might shed light on why the passenger plane nosedived into a remote mountainous area in southern China last week, killing all 132 people on board. (Huang Xiaobang/Xinhua via AP) (Huang Xiaobang/AP)
China Eastern Airlines crash investigation FILE - In this photo released by Xinhua News Agency, rescuers carry a piece of plane wreckage at the site of Monday's plane crash in Tengxian County, southern China's Guangxi Zhuang Autonomous Region, on March 25, 2022. The second “black box” has been recovered following the crash of a China Eastern Boeing 737-800 that killed 132 people last week, Chinese state media said Sunday, March 27. (Zhou Hua/Xinhua via AP, File) (Zhou Hua/AP)
China Eastern Airlines crash investigation CORRECTS NUMBER OF THE VICTIMS - In this photo released by Xinhua News Agency, search and rescuer workers conduct continued search operations at the China Eastern flight crash site in Tengxian County on Saturday, March 26, 2022, in southern China's Guangxi Zhuang Autonomous Region. The second "black box" has been recovered from the crash of a China Eastern Boeing 737-800 that killed 132 people last week, Chinese state media said Sunday. (Lu Boan/Xinhua via AP) (Lu Boan/AP)
China Eastern Airlines crash investigation CORRECTS NUMBER OF THE VICTIMS - In this photo released by Xinhua News Agency, a search and rescuer worker wearing a protective suit holds an umbrella using a tool to conduct a search operation at the China Eastern flight crash site in Tengxian County on Saturday, March 26, 2022, in southern China's Guangxi Zhuang Autonomous Region. The second "black box" has been recovered from the crash of a China Eastern Boeing 737-800 that killed 132 people last week, Chinese state media said Sunday. (Lu Boan/Xinhua via AP) (Lu Boan/AP)