The death toll at the Meethotamulla garbage dump has risen to 17 by this afternoon, the Police said. It said at least 13 people were injured in the mishap.
Meanwhile,Reuters said the estimated 300-foot (91 metre) dump collapsed after flames engulfed it late on Friday, the new year's day, and witnesses said around 100 houses could have been buried.
At least four teenagers were among the dead, a nurse at the main Colombo hospital has told Reuters.
"We heard a massive sound. It was like thunder. Tiles in our house got cracked. Black water started coming in," said Kularathna, who lives near the dump.
"We tried to get out but we were trapped inside. We shouted for help and were rescued later."
Another resident, Mohamed, said three of his neighbours were missing and estimated that more than 100 people could have been buried.
Rescue operations continued for a second day on Saturday with soldiers using heavy equipment to remove the garbage.
Police said about 145 houses had been damaged, but they did not say how many had been buried.
Residents of the area, mostly living in shanties, have been demanding the removal of the dump saying it was causing health issues.
The government had planned to remove it soon under an infrastructure plan.