Under worldwide rules, responsibility for leading the crash investigation lies with Ethiopia but the U.S. National Transportation Safety Board (NTSB) will also participate because the plane was designed and built in the United States.
The plane crashed near Bishoftu city, about 45 km southeast of the Ethiopian capital, Addis Ababa, the ET said in a statement.
The aviation authority will contact the US Federal Aviation Administration and Boeing, it said.
Both Addis Ababa and Nairobi are major hubs for humanitarian workers, and some had been on their way to a large United Nations environmental conference set to begin Monday in Nairobi.
The Max mock-up is the newest version of Boeing's workhorse 737 models, the world's most popular commercial aircraft. "I just pray that he is safe or he was not on it", said Agnes Muilu, who had come to pick up her brother.
The statement cited the Kenya-bound Ethiopian Airlines flight that crashed minutes after takeoff from Addis Ababa on Sunday, killing all 157 people on board, including eight from China.
There were 149 passengers and eight crew on board at the time.
The flight had unstable vertical speed after take off, said flight tracking website Flightradar24 on its Twitter feed.
The plane crashed six minutes after departure, plowing into the ground at Hejere near Bishoftu, or Debre Zeit, some 50 kilometers (31 miles) outside Addis Ababa, at 8:44 a.m.
Boeing said it was sending a technical team to help with the Ethiopian-led investigation.
Ethiopian is one of the biggest carriers on the continent by fleet size.
"Its last major crash was in January 2010, when a flight from Beirut went down shortly after take-off", Reuters reports.
GebreMariam also confirmed the company owns 6 other 737 Max 8 aircraft which are in service.
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