WASHINGTON — A political watchdog group called for investigations Monday to determine whether fundraisers for John McCain's presidential campaign arranged illegal "straw" donations — contributions from people who did not spend their own money.

Campaign Money Watch urged Attorney General Michael Mukasey to probe the activities of Florida defense contractor Harry Sargeant III, who is credited with raising more than $500,000 for the campaign. It also questioned $57,000 in donations from an office manager for the oil giant, the Hess Corp., and her husband, a railroad foreman.

The McCain campaign last week returned $50,000 of the donations tied to Sargeant, citing published reports that some California donors did not intend to vote for McCain. The campaign also sent a letter to others who contributed via Sargeant, stressing that only U.S. citizens or permanent residents may donate, and only if they use their own funds.