The gruesome findings on Thursday morning raise to at least 23 the number killed in the truck bombing.
UN spokesman Salim Lone said it was now unlikely anyone would be found alive.
"We hope until the bitter end to find someone, but it does not look good at this stage," he said.
No group has claimed responsibility for the bombing, the most devastating attack on a UN complex in the world body's 58-year history.
Meanwhile, UN Secretary-General Kofi Annan and US Secretary of State Colin Powell will meet on Thursday in New York to discuss a UN resolution that could provide greater security in Iraq.
"We hope until the bitter end to find someone, but it does not look good at this stage"
A senior US official in Washington said they would discuss how international efforts to end the chaos that has gripped Iraq could be boosted.
The United States is searching for a way to encourage other nations to commit more troops to Iraq to provide security for humanitarian work.
However, it still insists on remaining firmly in control of the occupation and reconstruction of the country.
"The basic strategy is to say that rather than pulling back when we're attacked, we need to push forward," said the official.