The landfill is called Koshe, which means "dust." It's been around for decades, servicing the sprawling and growing capital.
"It's a sad story because the government has been trying to resettle the people residing in the area," Communications Minister Negeri Lencho said. The government had also been building a factory to convert waste products at the landfill into energy, he said.
Fisseha Tekle, the chief researcher for Amnesty International in Ethiopia, said the government claims it has been developing for the last decade, "but it was not able to take residents out of this deplorable situation," he said.
And, he said, there had been no concrete action to remove the people from this area prior to this incident.
The smells permeate the landfill and nearby areas. Small fires erupt because of the methane gas the decomposing trash produces.
"And those people are living in the middle of that location. It's not a landfill anymore, it's like a mountain," Tekle said. "Whatever kind of country you are, you cannot let people live in this situation."
Tekle said the government should resettle the people and do an "accountability investigation."
The government is "fully responsible for the people living on this site and for their condition of those people who died, and for their lack of safety," he said.
Along with the dead, dozens were injured in the landslide, Lencho said. Video showed crews with heavy equipment at the scene scraping and digging through the debris and shots of flimsy and upended dwellings.
Investigators were trying to determine the cause and security personnel were still searching for people who have been reported missing in the landslide, Lencho said.
Authorities are working to find housing for the families affected.
The government has transferred 290 people who were living on the landfill, but who were not injured in the accident, to a temporary shelter in a youth center in Addis Ababa.
Many people at the landfill were "frantically looking for friends and family," Hope for Korah, a Canadian NGO that assists people living in the area near the dump, said on its Facebook page
Some of the people who were trapped in the landslide tried to call authorities to get help from inside the debris, the group said.
One woman and her three children managed to scramble to safety just as their home became caught up in the landslide, according to the NGO.
A similar landslide occurred in
December 2015 at a waste dump in Shenzhen, China
, killing 58.