Boeing 737 jets are being grounded after an Ethiopian Airlines crash. Here’s what you need to know.

China grounded all Boeing 737 Max 8 planes Monday after an Ethiopian Airlines jet crashed over the weekend killing all 157 people on board.

Sunday‘s disaster was the second fatal accident involving the new Boeing model in the past five months.

Flight ET302 crashed six minutes after taking off from Addis Adiba Sunday morning on its way to Nairobi.

The cause has yet to be established, but several airlines have pulled the 737 Max 8 from service as a precaution. Ethiopian Airlines announced Monday it was also grounding its fleet of four 737 Max 8 aircraft.

“At this stage, we cannot rule out anything,” Ethiopian Airlines CEO Tewolde Gebremariam told reporters at Bole International Airport in the capital.

The Civil Aviation Administration of China ordered all domestic carriers to ground Boeing 737 MAX 8 jets by 6 p.m. local time Monday, saying it had a “zero tolerance for safety hazards.”

The similarities between Sunday’s incident and a Lion Air accident in October — when a 737 Max 8 crashed after takeoff killing 189 people — prompted experts to call the incidents “highly suspicious.”

“Here we have a brand-new aircraft that's gone down twice in a year. That rings alarm bells in the aviation industry, because that just doesn't happen," Mary Schiavo, a former inspector general of the U.S. Transportation Department told CNN.

Flight ET302 took off from Bole International airport, bound for the Kenyan capital at 8:38 a.m. local time (0.38 a.m. ET). Six minutes later the Boeing 737 Max 8 came down near the town of Bishoftu, just 37 miles southeast of Addis Adiba.

All 149 passengers and 8 crew members were killed.

The pilot, captain Yared Getachew, had signaled he was experiencing technical difficulties shortly after launch and requested to return to the airport.

Flight-crash investigators are trying to piece together what happened, but so far no official explanation has been given. Weather conditions in the Ethiopian capital were perfect.

Ethiopian state media reported Monday that investigators had recovered the black box flight recorder.

Ethiopian airlines said Getachew had an “excellent flying record,” logging more than 8,000 hours.

The plane was delivered to Ethiopian Airlines in November and the airline said no technical issues had been flagged during routine checks.

“As I said, it is a brand-new airplane with no technical remarks, flown by a senior pilot and there is no cause that we can attribute at this time,” Gebremariam told reporters Sunday.

Flight-tracking website Flightradar24 tweeted that its data showed that “vertical speed was unstable after takeoff.” An eyewitness told CNN they saw smoke coming from the plane before it crashed on Sunday.

The Kenyan and Ethiopian governments announced a joint disaster response team Monday to investigate the crash. The U.S. National Transportation Safety Board is also sending a team of four to assist in the probe.

The plane was carrying passengers from 33 nationalities.

According to the airline, there were 32 Kenyans, 18 Canadians, nine Ethiopians, and eight people each from Italy, China and the U.S.

At least 19 of those on board were affiliated with the United Nations, many of whom were delegates on their way to the U.N. environment assembly, which was scheduled to begin in Nairobi Monday.

Italian archeologist Sebastiano Tusa, 66, was killed in the crash, and Slovakian lawmaker Anton Hrnko announced on Facebook that his wife, son and daughter had all died.

Greek Antonis Mavropoulos revealed on Facebook that he was due to fly to Nairobi but missed the flight by two minutes after arriving late at the gate.

"I was angry because nobody helped me to reach the gate on time," he wrote. "I'm grateful to be alive."

The Max 8 is the newest version of Boeing's most popular plane, and there are more 300 in use around the world.

Along with China and Ethiopian Airlines, Cayman Airlines announced it had grounded its fleet of two 737 Max 8 planes Monday “until more information is received.”

While there is no indication of what caused the disaster, similarities to a crash last year have raised concerns about the model’s safety.

In October, a 737 Max 8 operated by Lion Air crashed into the Java Sea soon after takeoff, killing all 189 people on board. An investigation into that crash is ongoing.

Boeing insists its planes are safe, and in a Sunday statement said a technical team will be traveling to the crash site to provide assistance. Sales of the 737 Max 8 have not suffered since the Lion Air disaster, and the company’s share price has soared.

Cover image: This picture taken on March 11, 2019, shows debris of the crashed airplane of Ethiopia Airlines, near Bishoftu, Ethiopia. (MICHAEL TEWELDE/AFP/Getty Images)