Addis Ababa, Ethiopia — An Ethiopian Airlines flight crashed shortly after takeoff from Ethiopia's capital Sunday morning, killing all 157 on board, authorities said, as grieving families rushed to airports in Addis Ababa and the destination, Nairobi. More than 30 nationalities are among the dead, including at least eight Americans.

It was not immediately clear what caused the crash of the Boeing 737-8 MAX plane, which was new and had been delivered to the airline in November. The pilot of Flight ET 302 sent out a distress call and was given clearance to return, the airline's CEO told reporters.

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.

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"Ethiopian Airlines is one of the safest airlines in the world. At this stage we cannot rule out anything," CEO Tewolde Gebremariam told reporters. He visited the crash site, standing in the gaping crater flecked with debris.

Black body bags were spread out nearby while Red Cross and other workers looked for remains. As the sun set, the airline's chief operating officer said the plane's flight data recorder had not yet been found.

Rescue team walk past collected bodies in bags at the crash site of Ethiopia Airlines near Bishoftu, a town some 32 miles southeast of Addis Ababa, Ethiopia, on Sun., March 10, 2019. Getty

The airline said 149 passengers and eight crew members were thought to be on the plane. Kenyans, Canadians, Chinese, Americans, Ethiopians, Italians, French, British, Egyptians, Indians, Slovakians and others were among the dead, according to Gebremariam.

The U.S. Department of State confirmed Americans were among the dead in a statement late Sunday.

"We can confirm that at least eight U.S. citizens were among the victims. Our embassies in Addis Ababa and Nairobi, in coordination with the U.S. National Transportation Safety Board, are working with the Government of Ethiopia and Ethiopian Airlines to offer all possible assistance," the State Department said. "Our teams in Addis Ababa, Nairobi, and Washington, D.C. are working tirelessly to provide all appropriate consular assistance to families of the victims at this difficult time."

A man carries a piece of debris on his head at the crash site of a Nairobi-bound Ethiopian Airlines flight near Bishoftu, a town some 37 miles southeast of Addis Ababa, Ethiopia, on Sun., March 10, 2019. Getty

The plane crashed six minutes after departing Addis Ababa on its way to Kenya's capital, plowing into the ground at Hejere near Bishoftu, or Debre Zeit, some 31 miles south of Addis Ababa, at 8:44 a.m.

The airline later published a photo showing its CEO standing in the wreckage. Little of the plane could be seen in the freshly churned Earth, under a blue sky.

"Tewolde Gebremariam, who is at the accident scene now, regrets to confirm that there are no survivors," the post on social media said. "He expresses his profound sympathy and condolences to the families and loved ones of passengers and crew who lost their lives in this tragic accident."

Accident Bulletin no. 2

Issued on march 10, 2019 at 01:46 PM pic.twitter.com/KFKX6h2mxJ — Ethiopian Airlines (@flyethiopian) March 10, 2019

The plane had showed unstable vertical speed after takeoff, air traffic monitor Flightradar 24 said in a Twitter post. Visibility was clear.

The U.S. National Transportation Safety Board said it is sending a team of four to assist in the investigation.

Victims mourned

State broadcaster EBC reported 33 nationalities were among the victims. The airline's CEO said those included 32 Kenyans and nine Ethiopians. Authorities said other victims include 18 Canadians; eight each from China, the United States and Italy; seven each from France and Britain; six from Egypt; five from the Netherlands and four each from India and Slovakia.

The airline has said 157 people were thought to be on board.

The Ethiopian prime minister's office offered its "deepest condolences" to families. "My prayers go to all the families and associates of those on board," Kenya's President Uhuru Kenyatta said.

Prime Minister Justin Trudeau on Sunday deplored the "devastating news" that 18 Canadian nationals were among those killed.

"Devastating news from Ethiopia this morning," Trudeau tweeted. "Our thoughts are with all the victims on Flight ET302, including the Canadians who were on board."

Canadians join people around the world in mourning the loss of so many lives today. Our hearts are breaking for the families and friends of the 18 Canadians who were killed. Please read my full statement on the tragic plane crash in Ethiopia: https://t.co/FG3wVmu5m8 — Justin Trudeau (@JustinTrudeau) March 10, 2019

His office later issued a statement. "We join the international community in mourning the loss of so many lives, including those countries who have also lost citizens in this devastating crash.

"I am reaching out to President of Kenya Uhuru Kenyatta and Prime Minister of Ethiopia Abiy Ahmed to express my condolences for this tragic event."

Nigeria's foreign affairs ministry said a former ambassador is among the victims of the Ethiopian Airlines crash. A statement said Abiodun Oluremi Bashua was a retired career envoy who served in various capacities in Iran, Austria and Ivory Coast.

It said the ambassador, born in 1951, was a "seasoned U.N. expert" with experience in several United Nations peacekeeping missions in Africa.

The World Food Program (WFP) is confirming that two of the eight Italian victims aboard the Ethiopian Airlines jet worked for the Rome-based U.N. agency. A WFP spokeswoman identified the victims as Virginia Chimenti and Maria Pilar Buzzetti.

Another three Italians worked for the Bergamo-based humanitarian agency Africa Tremila: Carlo Spini, his wife Gabriella Viggiani and the treasurer, Matteo Ravasio.

In addition, Paolo Dieci, a prominent aid advocate with the International Committee for the Development of Peoples, known by its acronym CISP, was killed.

Also among the Italian dead was Sebastiano Tusa, a noted underwater archaeologist and the Sicilian regional assessor at the Culture Ministry. RAI state television said he was heading to Malindi, Kenya to participate in a UNESCO conference on safeguarding underwater cultural heritage in east Africa, which opens Monday.

Another victim was from the Save the Children, an organization that promotes children's rights.

"It is with profound sadness that Save the Children confirms the loss of one of our colleagues, Tamirat Mulu Demessie, in the crash of Ethiopian Airlines Flight 302 ..." the statement said. "Tamirat served as a Child Protection in Emergencies Technical Adviser, and worked tirelessly to ensure that vulnerable children are safe during humanitarian crises. Our thoughts are with Tamirat's family and the loved ones of the 156 other people who lost their lives in this terrible tragedy."

Family members arrive at Bole International airport in Addis Ababa, Ethiopia, on Sunday, March 10, 2019. AP

Victims' families react to the crash

The Addis Ababa-Nairobi route links East Africa's two largest economic powers and is popular with tourists making their way to safari and other destinations. Sunburned travelers and tour groups crowd the Addis Ababa airport's waiting areas, along with businessmen from China and elsewhere.

At the airport in Nairobi, worried families gathered.

"I came to the airport to receive my brother but I have been told there is a problem," Agnes Muilu said. "I just pray that he is safe or he was not on it."

"Why are they taking us round and round, it is all over the news that the plane crashed," said Edwin Ong'undi, who had been waiting for his sister. "All we are asking for is information to know about their fate."

Boeing 737-8 MAX recent disasters

The Boeing 737-8 MAX was new, delivered to Ethiopian Airlines in mid-November, the airline's CEO said. Its last maintenance was Feb. 4 and it had flown just 1,200 hours. The pilot was a senior one, joining the airline in 2010, he said.

In a statement, Boeing said it was "deeply saddened" to hear of the crash and that a technical team was ready to provide assistance at the request of the U.S. National Transportation Safety Board.

In October, another Boeing 737-8 MAX plunged into the Java Sea just minutes after taking off from Jakarta, Indonesia's capital, killing all 189 people on board the plane Lion Air flight. The cockpit data recorder showed that the jet's airspeed indicator had malfunctioned on its last four flights, though Lion Air initially claimed that problems with the aircraft had been fixed.

The last deadly crash of an Ethiopian Airlines passenger plane was in 2010, when the plane crashed minutes after takeoff from Beirut killing all 90 people on board.

Sunday's crash comes as the country's reformist prime minister, Abiy Ahmed, has vowed to open up the airline and other sectors to foreign investment in a major transformation of the state-centered economy.

Ethiopian Airlines has been expanding assertively, recently opening a route to Moscow and in January inaugurating a new passenger terminal in Addis Ababa to triple capacity.

Speaking at the inauguration, the prime minister challenged the airline to build a new "Airport City" terminal in Bishoftu — where Sunday's crash occurred.