A key lawmaker sent a letter Wednesday to U.N. Secretary General Kofi Annan (search) asking for the immediate release of 55 internal audits of the controversial Iraqi oil-for-food program (search).

Rep. Henry Hyde (search), chairman of the House International Relations Committee, sent the letter after Fox News reported on a leaked audit from April 2003 that found significant problems with the program. Specifically, the audit raised questions about a company that employed Annan's son as it prepared to bid an oil-for-food contract.

Hyde wrote to Annan that he had a "deep concern" about the audit's conclusions and he noted that Congress "should not be required to depend on media leaks for source documents."

Click to read the letter from Rep. Hyde to Kofi Annan (pdf).

Click to read letters from Benon Sevan, Cotecna (pdf).

Click to read the U.N. internal audit of the oil-for-food program (pdf).

To deal with the allegations that companies and individuals — including former Iraqi dictator Saddam Hussein — siphoned off billions of dollars meant for the Iraqi people, Annan named a three-member panel led by Paul Volcker to lead an investigation. Volcker is the respected former chairman of the U.S. Federal Reserve.

Annan has said that he expects Benon Sevan, the former head of the program, and other U.N. staff members to cooperate with the investigation. But Sevan's office has sent letters to some of the companies involved in the program not to release any documents or to talk to investigators without prior approval.

One of the companies that received the letter is Cotecna, the Swiss-based company that was awarded a $4.8 billion contract for the oil-for-food program just months after Annan's son, Kojo, ended a consulting assignment with the firm.

Fox News has obtained a letter sent April 13 from Cotecna's senior vice president, Andre E. Pruniaux, asking Sevan for permission to cooperate with investigators. The letter was a follow-up to an April 8 letter Pruniaux wrote saying that U.S. governmental authorities, including a House subcommittee on the Middle East and Central Asia, had contacted the company for information.

"At this juncture, we believe it would be most beneficial to all involved to respond to such requests by authorities in order to explain Cotecna's limited, technical role in the Programme, thereby dismissing any suggestion of impropriety in recent reports by the media," Pruniaux wrote.

It is not clear if U.N. officials responded to Pruniaux or gave the company the authorization to cooperate with investigators.

Cotenca officials have declined to answer individual questions about the company's participation in the program or the role of Kojo Annan. In the past, they've issued statements denying any wrongdoing and maintaining that they properly followed all U.N. regulations.

Sevan has denied any impropriety with his management of the oil-for-food program and has said he would cooperate with investigators.

When confronted by Fox News on Thursday outside the United Nations, Sevan refused to answer questions about whether he profited personally or about his discussions with Annan and Volcker.

Fox News' Jonathan Hunt contributed to this report.