A China Eastern Airlines Boeing 737-800 with 132 people on board plunged midflight and crashed in a mountainous area of southern China on Monday, according to officials and flight-tracking data.

Flight MU5735 left Kunming at 1:11 p.m. local time (1:11 a.m. ET) and was due to arrive at Guangzhou in the southeast of the country in less than two hours, according to information on FlightRadar24.

The plane was cruising at 29,100 feet and began a sharp descent after 2:20 p.m., recovering briefly then resuming the dive before it lost contact. It fell more than 25,000 feet in about two minutes.

“This kind of tragedy is extremely unusual,” Richard Aboulafia, a managing director at AeroDynamic Advisory, said of the plane’s sudden, sharp drop from its cruising altitude.

China’s Civil Aviation Administration said it was sending a team to the crash site in the Guangxi region.

Chinese state media said the crash had caused a mountain fire. Video circulating on social media showed fire and smoke in the mountains and a section of a plane near a dirt path. Chinese officials have yet to confirm any passenger deaths.

The 737-800 is one of the world’s most common jetliners. The one that crashed Monday in China first flew in June 2015. It was not a Boeing 737 Max, the plane that was grounded worldwide after two fatal crashes in 2018 and 2019.

China Eastern Airlines confirmed the crash and the number of people on board via a statement on Weibo, which is China’s version of Twitter. The airline said it is sending workers to the site of the crash and has opened a hotline for family members.

The U.S. Federal Aviation Administration said it is “aware of reports that a China Eastern Airlines Boeing 737-800 plane crashed this morning in China.”

“The agency is ready to assist in investigation efforts if asked,” the FAA said in a statement.

Boeing said it was “aware of the initial media reports” and is gathering more information.

Typically when a crash takes place, the country where the crash occurs leads the investigation, but Boeing as the manufacturer and its regulator, the FAA, will also likely be involved.

“We are deeply saddened by the tragic news of China Eastern flight MU5735. We extend our heartfelt sympathies to the families and the loved ones of those on board,” said CFM International, a joint venture of General Electric and France’s Safran, which makes the engines for the planes.

China Eastern changed the colors of its website to black and white — something airlines do following a crash out of respect for passengers’ families.

Chinese President Xi Jinping said he was “shocked” to learn of the incident, according to state media CCTV. He instructed Shanghai-based China Eastern to organize search and rescue efforts and begin an investigation into the cause of the crash.

The last serious passenger plane crash in China was in 2010, when 42 people died on a Henan Airlines Embraer E-190 flight.

Boeing shares were down more than 4% in morning trading on Monday.

There are more than 4,200 737-800s in service worldwide and 1,177 in Chinese airlines’ fleets — the most of any country — according to aviation data and consulting firm Cirium.

Boeing has been trying to recover its reputation after the two crashes of the Max. The Boeing 737 Max was grounded worldwide in March 2019 after the second of the two crashes, occurring within five months of one another.

Indonesia’s Lion Air Flight 610 crashed on Oct. 29, 2018, and Ethiopian Airlines Flight 302 went down on March 10, 2019. All 346 people on board the two flights were killed in the crashes. 

China was the first country to ground the Max after the second crash. The U.S. and most other countries cleared the planes to return to service more than a year ago. Chinese regulators allowed the Max to resume flying in December, with changes, but the planes have not yet returned to service.

Monday’s crash was a 737NG, or next generation, the model before the 737 Max.

Boeing reported its third annual loss in a row in January, disclosing $5.5 billion in costs tied to manufacturing flaws, which have forced the company to pause deliveries of the company’s 787 Dreamliners for most of the last 17 months.