Search goes on for 2nd black box in China Eastern Airlines crash

The commercial passenger jet that crashed Monday in southern China plunged into a mountainside with such force it created a 66-foot deep crater and shattered into pieces, officials said Thursday.

Search crews have recovered 183 pieces of the China Eastern Airlines plane and the remains of 21 of the 132 people killed in the air disaster, Zhu Tao, director of the Aviation Safety Office of the Civil Aviation Administration of China, said at a news conference.

One piece of the aircraft roughly 4 feet long and 4 inches wide was found on farmland 6.2 miles from the core crash site in China's Guangxi region. Officials would not speculate on how it ended up there but said they are expanding the search area.

Zhu said search crews were still looking Thursday for the Boeing 737-800's second black box, believed to be the flight data recorder that was installed above the ceiling of the aircraft's rear cabin.

The plane's cockpit voice recorder, installed in the plane's rear cargo compartment, was recovered from the wreckage on Wednesday and is expected to be analyzed at a lab, officials said.

Zhu said most of the wreckage of Flight 5735 is concentrated in and around an impact crater measuring nearly 100 feet wide and 66 feet deep.

Among the pieces recovered are an engine blade and engine pylon, the left and right horizontal stabilizers, pieces of the wings and the plane's aileron autopilot actuators.

"We also found crew escape ropes and fragments of crew manuals and some crew documents normally found in the cockpit," Zhu said.

The cause of the crash remains under investigation.

The plane crashed after taking off from Kunming, the capital of China's Yunnan province. The flight was headed to Guangzhou, a port city northwest of Hong Kong, Chinese officials said.

Early data shows the airliner plunged from 29,000 feet to 8,000 feet, leveled off and then went into a freefall, exploding into a fireball that was seen and filmed by people nearby. One video showed the plane nose-diving into the ground.

Air traffic controllers made repeated attempts to radio the flight crew when they noticed the aircraft's rapid descent but were unable to restore communications with the crew before the crash, Chinese officials said.

U.S. intelligence doesn’t have a clear theory on what led to the plane crashing. A source tells ABC News they aren’t ruling anything out, including a possible intentional downing.

During Thursday's news conference, Chinese officials said more than 300 family members of passengers on the doomed plane were gathered in Wuzhou in the Guangxi region and that China Eastern Airlines had dispatched 161 staff members to meet with them and provide assistance and comfort. More than 200 of the family members have been taken near the crash scene to mourn their lost loved ones, officials said.