One of two "black box" recorders from a China Eastern passenger plane that crashed in southern China on Monday with 132 people on board has been found, a Chinese aviation official said on Wednesday. The retrieval of so-called black box recorders following a crash is considered a key element in finding out the cause.  Investigators say the believe the one they found is the cockpit recorder, which captures sounds, including conversations and background engine noise, during the flight. The second type of black box is the flight data recorder, which captures information about the plane's airspeed, altitude, direction up or down, pilot actions, and performance of all key systems.   The outer casing of the recorder and its storage component both suffered damage, but the unit itself was "relatively intact," Zhu Tao, director of the Office of Aviation Safety at the Civil Aviation Authority of China, told reporters at a briefing. Zhu said the recorder would be sent to Beijing for decoding and analysis. It's still unclear how long that will take, as it depends on the degree of damage the unit suffered, he added. Investigators will next "continue to go all-out to find the flight data recorder to provide even more comprehensive data support to reconstruct the entire incident," he said. China Eastern Flight 5735, a Boeing 737-800, was carrying 123 passengers and nine crew from Kunming in Yunnan province to Guangzhou on China's southeastern coast. It crashed on Monday afternoon outside the city of Wuzhou in the Guangxi region with all 132 people on board presumed killed, making it China's worst crash in more than a decade. To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video The plane went into an unexplained dive an hour after departure and stopped transmitting data 96 seconds into the fall, with aviation officials still mystified as to the cause of what seems to be an unmotivated descent. Mao and other officials at Wednesday's news conference said the aircraft had a clean maintenance record, the weather had been good during the flight and the crew had been in regular communication with air traffic controllers before the dive commenced. Shanghai-headquartered China Eastern is one of China's three largest carriers with more and has 109 Boeing 737-800s in its fleet. The aircraft has been flying since 1998 and has a good safety record. fb, tj/wmr (AP, AFP)