WASHINGTON – Amid mounting allegations of fraud and incompetence involving the Red Cross, and on the heels of its president’s abrupt resignation, Senator Grassley, a Republican of Iowa, demanded answers from America’s largest relief organization yesterday while announcing plans to probe the charity’s operations, governance, and finances.

“The response to Katrina and the recent resignation of the President and CEO of the Red Cross have understandably raised questions about the Red Cross,” Mr. Grassley wrote in a letter sent yesterday to the chairman of the charity’s board of governors, Bonnie McElveen-Hunter. “Given that the Red Cross is a tax-exempt organization, chartered by Congress … it is the duty of Congress to engage in oversight to ensure that the Red Cross is performing its role effectively,” he wrote.

Mr. Grassley’s letter includes requests for all internal communications between the Red Cross’s president and board members, all internal audits, and Internal Revenue Service filings for the last five years. Mr. Grassley also demands an explanation of the Red Cross’s holdings in a Bermuda-based insurance company.

Mr. Grassley is chairman of the Senate Finance Committee, which has oversight of tax-exempt charities. The senator has investigated the Red Cross in the past, notably after donations intended for victims of the September 11, 2001, attacks were directed to unrelated Red Cross work.

Hurricane Katrina prompted new concerns about the organization, as reports surfaced of lax oversight of relief efforts. Last week, 50 people, including 17 Red Cross workers, were indicted for scamming hundreds of thousands of dollars from a Katrina relief program. Earlier this month, the then president of the Red Cross, Marsha Evans, resigned hours before a House hearing meant to probe charities’ responses to Katrina. Red Cross officials attributed her departure to conflict with the organization’s board.

To Mr. Grassley, however, that explanation raised more questions than it answered. “When a spokesman for one of the most prominent charities in the world cited ‘coordination and communication issues with the board’ as the reason for Ms. Evans’ departure, I really have to question what exactly has been going on for the last several years,” the senator said in an e-mailed statement to The New York Sun.

In a response statement issued by the Red Cross yesterday, the organization said it “looks forward to the opportunity to dialogue with members of the committee on how we can better fulfill our Congressionally-mandated mission moving forward,” and promised to respond to the Finance Committee’s questions by the January 30 deadline set by Mr. Grassley in the letter.