One witness said the ill-fated Ethiopian Airlines Boeing 737 MAX 8 was already on fire - and swerving erratically - before it crashed, 60km from Addis Ababa.
"The plane was already on fire when it crashed to the ground. The crash caused a big explosion," said witness Tegegn Dechasa at the site.
Another, farmer Sisay Gemechu, said: "The plane seemed to be aiming to land at a nearby level open field, but crashed before reaching there."
Ethiopia and China grounded fleets of Boeing 737 MAX 8 after the crash of a new passenger jet that killed all 157 people on board as the search resumed on Monday for bodies and clues into the disaster.
Ethiopia's parliament declared on Monday a day of mourning over the crash of the Ethiopian Airlines jet, which ploughed into a field some 60km east of Addis Ababa on Sunday - just six minutes after taking off from the capital on a flight to Nairobi.
Plane debris, passenger belongings and human remains
As inhabitants of the remote, rural part of Ethiopia looked on from behind a security cordon, inspectors early on Monday searched the site for plane debris, passenger belongings and human remains.
The single-aisle Boeing left a deep, black crater at the impact site, which was being dug up with a mechanical excavator.
Ethiopian Airlines, Africa's largest carrier, said on Monday it was grounding its remaining fleet of six 737 MAX 8 Boeings "until further notice".
China, too, ordered domestic airlines to suspend commercial operation of the Boeing 737 MAX 8. The country had eight nationals among the 157 people - 149 passengers and eight crew - aboard the ill-fated flight ET 302.
Boeing has described the MAX series as its fastest-selling airplane ever, with more than 4 500 orders placed by July 2018 from 99 customers worldwide.
State-owned Ethiopian Airlines had ordered 30.
The plane that crashed Sunday was new, delivered to Ethiopia on November 15, the carrier said.
It is the same type as the Indonesian Lion Air jet that crashed in October, 13 minutes after take-off from Jakarta, killing all 189 people from 35 countries on board.
At least 22 UN staff were on the flight, many headed for an annual assembly of the UN Environment Programme which opened under a dark cloud in Nairobi on Monday.
UN flag flying at half-mast
Delegates arrived with the UN flag flying at half-mast, hugging and comforting one another as they wondered who among the staff may have been on the plane.
"Let us reflect that our colleagues were willing to travel and to work far from their homes and loved ones to make the world a better place to live," UN Habitat head Maimunah Sharif told some of those gathered.
Among the dead were staff from the World Food Programme, the UN refugee agency (UNHCR), the International Organization for Migration, and Food and Agriculture Organization, the agencies said.
Nairobi hosts the global headquarters of UNEP and UN Habitat, and is the regional seat of several other UN agencies.
"Deeply saddened by the news this morning of the plane crash in Ethiopia, claiming the lives of all on board," tweeted UN Secretary General Antonio Guterres.
Ethiopian Airlines CEO Tewolde GebreMariam said the plane had flown in from Johannesburg earlier Sunday, spent three hours in Addis and was "despatched with no remark", meaning no problems were flagged.
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