The death toll from Friday's collapse in the capital Colombo has risen to 26, including six children, the army says.
The 300ft (91m) high pile of rotting debris shifted after floods and a fire, destroying dozens of homes.
Residents had demanded for years the removal of the dump, saying it was causing health problems.
About a thousand people are thought to have been displaced by the disaster.
The government has now announced the closure of the Meethotamulla dump. Reports said 800 tonnes of waste were added to
it every day.
Many residents had left their homes before the collapse because of the heavy rain
President Maithripala Sirisena ordered hundreds of troops to search for survivors and bolster rescue efforts of the fire department.
The army said the operation would continue until all the missing were found.
"We expect we could complete this in the next 72 hours," .
Family members of victims react during a rescue mission after a garbage dump collapsed and buried dozens of houses in Colombo