The head of the Palestinian anti-corruption body said he has clawed back $70m in five years from officials who used state money to strike business deals abroad and then pocketed the profits.
But Rafiq al-Natsheh, chairman of the Palestinian Anti-Corruption Commission, told the Reuters news agency in an interview late on Tuesday that "tens of millions of dollars" still needed to be tracked down.
One of the biggest challenges for his team, he said, was finding money that had disappeared abroad.
Natsheh said his investigators had failed to uncover evidence to justify allegations that hundreds of millions of dollars in government funds had gone missing.
After years of talk of vast sums going astray, the attorney general of the Palestinian Authority announced in February 2006 that he was investigating 50 cases of embezzlement from the authority's budget totalling $700m.
President Mahmoud Abbas is under pressure from donors to show he is taking action.
The European Union and the United States, both of which give direct budget support to the Palestinians, want to see tighter controls, with the Europeans going as far as to send investigators to track where some of their money has gone.
Over the past five years, direct support to the Palestinian budget from the EU and others has fallen from around $1.3bn a year to less than $700m, with the decline attributed in large part to frustration over money not being spent where it was intended, or not being fully accounted for.
Natsheh was given sweeping powers to investigate misappropriation of funds, embezzlement, bribery, nepotism and any other corrupt practices.
The $70m recouped for the Palestinian Authority came from a series of successes against senior officials, including three ministers and a director general of the finance ministry, he said.
"We got $40m back from Egypt and $20m from Iraq," he said, describing deals in which Palestinian officials used state funds to do business abroad and pocketed the proceeds, rather than transferring them to the PA budget.
He mentioned a conviction handed down by the corruption court against an adviser to former president Yasser Arafat, but the $34m missing has not yet been recovered.
The same goes for a case involving $1m, and the former ambassador to Abu Dhabi was convicted of embezzling more than $2m.
"The biggest challenge we face is to get the money back," he said. "There are many millions outside Palestine, so it depends on foreign countries for us to get the money back."
Asked how much money was still outstanding, he talked of "tens of millions" of dollars, but wouldn't go into more detail.
"It's very stressful work, it's difficult," he said.