The aviation authority will contact the US Federal Aviation Administration and Boeing, it said.
At the Nairobi airport, hopes quickly dimmed for loved ones.
A general view shows the scene of the Ethiopian Airlines Flight ET 302 plane crash, near the town of Bishoftu, southeast of Addis Ababa, Ethiopia on March 10, 2019. "She's not picking up her phone", said Wendy Otieno, clutching her phone and weeping. GebreMariam said they have not yet determined the cause of the crash.
Investigators say that the pilots of the 737 Max-8 aircraft have been struggling with a new feature of the aircraft, which is an automated system created to keep the plane from stalling.
"At this time search and rescue operations are in progress and we have no confirmed information about survivors or any possible causalities", Ethiopian Airlines said in a statement. The Boeing 737 Max 8 was one of 30 meant for the airline, Boeing said in July.More news: Facebook sues Ukrainian app developers for scraping user data
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The country's state media, Fana Broadcasting Corporate, was quoted by Agence France-Presse (AFP) as saying that the plane, which departed the Ethiopian capital at 8:38 am, crashed minutes after takeoff, "killing all the 149 passengers and eight crew aboard".
The senior Ethiopian Airlines pilot had flown more than 8,000 hours. Boeing planned to send a technical team to Ethiopia.
In the USA, the Federal Aviation Administration said it would join the National Transportation Safety Board in assisting Ethiopian authorities with the crash investigation.
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 flight left Bole airport in Addis Ababa at 8.38 am local time, before losing contact with the control tower just a few minutes later at 8.44 am.