A China Eastern Airlines Boeing 737-800 crashed with 132 people on board — 123 passengers and nine crew members — China’s civil aviation authority said Monday.

Contact was lost with the flight over Wuzhou, in the mountainous Guangxi region, the agency said.

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 flight-tracking website shows the Boeing 737-800 plane plunged after 2-20 p.m. local time from 29,100 feet over the next two minutes.

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

The number of deaths is currently unknown.

China’s Civil Aviation Administration said it had “activated the emergency mechanism and dispatched a working group to the scene,” according to a translation.

Chinese state media said the crash had caused a mountain fire. Unconfirmed video circulating on social media showed fire and smoke in the mountains. Chinese officials have yet to confirm any passenger deaths.

China Eastern Airlines confirmed the crash and the number of people on board via a statement on Weibo, 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.

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 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 roughly 5% in premarket trading Monday.

The 737-800 is one of the world’s most common jetliners, with more than 4,200 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 two fatal crashes of its latest model of the 737, 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 came down on March 10, 2019, killing a combined 346 people.

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, not the more recent 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 hindered deliveries of the company’s 787 Dreamliner program.