"We are at 121 people found," Elisabeth Byrs, a spokeswoman for the UN's Organisation for the Coordination of Humanitarian Affairs, told AFP, describing it as a "miracle."
On Tuesday, the UN said 90 people had been extracted alive, compared to 70 on Saturday.
It was not immediately clear when the 31 extra survivors were pulled out. Experts said the chances of survival were greatly diminished three days after an earthquake.
Byrs said a second international relief operations centre was set up in the capital of the neighbouring Dominican Republic, Santo Domingo, alongside the one in Haiti's capital Port-au-Prince.
Three airports, as well as ports, in the Dominican Republic were being used for international aid deliveries, she added, to relieve bottlenecks that had stifled the relief effort over the past week.
Aid group Medecins Sans Frontieres (MSF - Doctors Without Borders) said on Tuesday that one of its planes carrying vital medical equipment to Haiti's quake victims had repeatedly been prevented from landing at Port-au-Prince.