A China Eastern Airlines passenger jet with 132 people on board crashed in the mountains of southern China on Monday while on a flight from the city of Kunming to Guangzhou, China's Civil Aviation Administration of China (CAAC) said.

The jet involved in the accident was a Boeing 737 aircraft and the number of casualties was not immediately known, state broadcaster CCTV said.

Rescue services were on their way to the scene, it said. There was no word on the cause of the crash.

The plane was a 6-year-old 737-800 aircraft, according to Flightradar24.

The CAAC said the aircraft lost contact over the city of Wuzhou. It had 123 passengers and nine crew on board. State media said earlier there were 133 people on board.

"The CAAC has activated the emergency mechanism and sent a working group to the scene," it said in a statement.

Media cited a rescue official as saying the plane had completely disintegrated. A fire sparked by the crash burned down bamboo and trees before being put out.

The flight departed the southwestern city of Kunming at 1:11 p.m. (0511 GMT), FlightRadar24 data showed, and had been due to land in Guangzhou, on the south coast, at 3:05 p.m. (0705 GMT).

The plane had been cruising at an altitude 29,100 feet at 0620 GMT, according to FlightRadar24 data.

Just over two minutes and 15 seconds later, the next available data showed it had descended to 9,075 feet. In another 20 seconds, its last tracked altitude was 3,225 feet.

The website of China Eastern Airlines was later presented in black and white, which airlines do in response to a crash as a sign of respect for the assumed victims. Boeing China's website also switched to black and white.

Shares of Boeing Co were down 6.4% at $180.44 in premarket trade. Boeing did not immediately respond to a request for comment.

Aviation data provider OAG said this month that state-owned China Eastern Airlines was the world's sixth-largest by scheduled weekly seat capacity and the biggest in China.

It has had a relatively strong performance in the domestic market during the coronavirus pandemic despite tight curbs on international flights, OAG said.

The safety record of China's airline industry has been among the best in the world over the past decade.

According to Aviation Safety Network, China's last fatal jet accident was in 2010, when 44 of 96 people on board were killed when an Embraer E-190 regional jet flown by Henan Airlines crashed on approach to Yichun airport in low visibility.

The 737-800 model that crashed on Monday has a good safety record and is the predecessor to the 737 MAX model that has been grounded in China for more than three years following fatal crashes in 2018 in Indonesia and 2019 in Ethiopia.

1994, a China Northwest Airlines Tupolev Tu-154 flying from Xian to Guangzhou was destroyed in an accident after takeoff, killing all 160 people on board and ranking as China's worst-ever air disaster, according to Aviation Safety Network.