Washington ? The Senate Finance committee has asked the IRS to turn over confidential tax and financial records, including donor lists, for dozens of Muslim charities and foundations as part of a widening congressional investigation into alleged ties between tax-exempt organizations and terrorist groups, according to documents and officials.

The request marks a rare and unusually broad use of the Finance committee’s power to obtain private financial records held by the government, and raises the possibility that individual contributors to the Holy Land Foundation or the activities of the Muslim Student Assn. could be subjected to Senate scrutiny.

The Senate-led probe follows more than two years of investigations by the FBI, Treasury Department and other federal agencies into the activities of Islamic charities suspected of having ties to al-Qaida, Hamas and other groups designated terrorist organizations by the U.S. government. The United States has frozen more than $136 million in assets allegedly linked to al-Qaida or other terrorist groups and has effectively shut down the operations of the largest U.S.-based Islamic charities.

“Government officials, investigations by federal agencies and the Congress and other reports have identified the crucial role that charities and foundations play in terror financing,” the committee’s leaders, Chairman Charles Grassley, R-Iowa, and Ranking Member Max Baucus, D-Mont., wrote in a Dec. 22 letter to the Internal Revenue Service.

“We have a responsibility to carry out oversight to ensure charities, foundations and other groups are abiding by the laws and regulations, to examine their source of funds, and to ensure government agencies, including the IRS, are policing them and enforcing the law efficiently and effectively.”