China's civilian aviation authority has ordered all Chinese airlines to temporarily ground their Boeing 737 Max 8 planes after one flying for Ethiopian Airlines crashed after taking off from Ethiopia's capital on Sunday, killing 157 people on board.

The passengers, who were from at least 35 countries, included three Austrian physicians, the co-founder of an international aid organization, a career ambassador, the wife and children of a Slovak legislator, a Nigerian-born Canadian college professor, eight Chinese nationals, and at least eight Americans, according to the airline.

The Civil Aviation Administration of China said the order to ground planes was issued at 9 a.m. Beijing time Monday and would last nine hours. It said the order was taken out of safety concerns because the Ethiopian crash was the second in similar circumstances since an Indonesian crash in October also killed everyone aboard.

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"Safety is our number one priority and we are taking every measure to fully understand all aspects of this accident, working closely with the investigating team and all regulatory authorities involved," Boeing said in a Monday statement.

The company added that the investigation is still in its early stages and there is no need to offer additional guidance to 737 MAX 8 aircraft operators, Reuters reported.

Body bags were spread out nearby while Red Cross and other workers looked for remains.

Around the world, families were gripped by grief. At the Addis Ababa airport, a woman called a phone number in vain. “Where are you, my son?” she said, in tears. Others cried as they approached the terminal.

At the Nairobi airport, hopes quickly dimmed for loved ones. “I just pray that he is safe or he was not on it,” said Agnes Muilu, who had come to pick up her brother.

Henom Esayas, whose sister’s husband was killed, told The Associated Press they were startled when a stranger picked up their frantic calls to his phone, told them he had found it in the debris and promptly switched it off.

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The father of a British woman named Joanna Toole has told the DevonLive website that he was informed she'd died in the crash.

Adrian Toole said his 36-year-old daughter Joanna was traveling for her work for the United Nations.

He told the website she was a fervent environmentalist who had worked on animal welfare issues since she was a child.

He said, “Joanna’s work was not a job, it was her vocation.”

Toole said his daughter used to bring home pigeons and rats in need of care and had traveled to the remote Faroe Islands to try to stop whaling there.

She is one of seven British nationals confirmed to have died in the crash.

According to her Facebook page, she worked for the U.N.’s Food and Agriculture Organization.

Another victim, Cedric Asiavugwa, a law student at Georgetown University in Washington, D.C., was on his way to Nairobi after the death of his fiancee's mother, the university said in a statement.

Asiavugwa, who was in his third year at the law school, was born and raised in Mombasa, Kenya. Before he came to Georgetown, he worked with groups helping refugees in Zimbabwe, Kenya, Uganda and Tanzania, the university said, adding that his family and friends "remembered him as a kind, compassionate and gentle soul, known for his beautifully warm and infectious smile."

Shocked leaders of the United Nations, the U.N. refugee agency and the World Food Program announced that colleagues had been on the plane. The U.N. migration agency estimated some 19 U.N.-affiliated employees were killed. Both Addis Ababa and Nairobi are major hubs for humanitarian workers, and many people were on their way to a large U.N. environmental conference set to begin Monday in Nairobi.

The Addis Ababa-Nairobi route links East Africa’s two largest economic powers. Travelers and tour groups crowd the Addis Ababa airport’s waiting areas, along with businessmen from China, Gulf nations and elsewhere.

A list of the dead released by Ethiopian Airlines included passengers from China, the United States, Saudi Arabia, Nepal, Israel, India and Somalia. Kenya lost 32 citizens. Canada, 18. Several countries including the United States lost four or more people.

The State Department said it would contact victims’ family members directly and that “out of respect for the privacy of the families, we won’t have any additional comments about the victims.”

A brief State Department statement said U.S. embassies in Addis Ababa and Nairobi were working with Ethiopia’s government and Ethiopian Airlines “to offer all possible assistance.”

Ethiopian officials declared Monday a day of mourning.

The Ethiopian plane was new, delivered to the airline in November. The Boeing 737 Max 8 was one of 30 meant for the airline, Boeing said in July. The jet’s last maintenance was on Feb. 4, and it had flown just 1,200 hours.

The plane crashed six minutes after departure, plowing into the ground at Hejere near Bishoftu, or Debre Zeit, some 31 miles outside Addis Ababa, at 8:44 a.m.

There was no immediate indication why the plane went down in clear weather while on a flight to Nairobi, the capital of neighboring Kenya.

In the U.S., the Federal Aviation Administration said it would join the National Transportation Safety Board in assisting Ethiopian authorities with the crash investigation. Boeing planned to send a technical team to Ethiopia.

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The crash shattered more than two years of relative calm in African skies, where travel had long been chaotic. It also was a serious blow to state-owned Ethiopian Airlines, which has expanded to become the continent’s largest and best-managed carrier and turned Addis Ababa into the gateway to Africa.

African air travel has improved in recent years, with the International Air Transport Association in November noting “two years free of any fatalities on any aircraft type.”

The Associated Press contributed to this report.

Fox News' Bradford Betz contributed to this report.