The US Treasury said banks were still "scouring their accounts" for any further funds connected to Muammar Gaddafi, as the US government seeks to put further pressure on his regime.
They have already blocked accounts of the Libyan Investment Authority, which is the sovereign wealth fund, and have frozen assets of the Libyan Central Bank, believed to be controlled by Colonel Gaddafi and his family.
In a Treasury briefing, financial intelligence official David Cohen did not name any banks or the number of banks with accounts, but said they were at "many major institutions"
A Libyan Central Bank building in Tripoli: its assets held in the US are blocked
The US order comes after the British government announced it too was taking action to freeze Gaddafi's assets in the UK so they could not be used against the interests of the Libyan people.
"These blocking actions by the United States and the UN, UK and EU, serve two very important objectives: depriving Colonel Gaddafi and his government of access to these assets and simultaneously safeguarding them for the Libyan people," said Mr Cohen.
As the search for any of Gaddafi's remaining money continues, forensic investigator Craig Scarr warned that the length of the Libyan leader's rule could complicate efforts to trace his cash.
Speaking on Jeff Randall Live, he said: "The problem comes when you're looking at a very long-standing regime where a high proportion of the time that regime has been recognised and accepted as a trading or investment partner."
Mr Scarr, who has previously worked with the FBI and Serious Fraud Office, explained that while Gaddafi clung on to power, investigators would be looking for two types of assets.
"The first is visible assets, where investments have been made when the regime was recognised," he said.
"Then when regimes get nervous about long-term recognition, they start moving into shadow assets, where investments are made on behalf of those people.
"That's when the investigation really gets interesting."
Mr Scarr added that attention would turn straight to Libyan records if and when Gaddafi fell, but he warned that by this time the paper trail may have gone cold.
"The objective is to repatriate the funds back to the people of Libya," he said, adding there was a "good possibility" that millions of pounds of their money had gone missing.
