WASHINGTON —  Two senators have asked the Pentagon to reopen the investigation into Air Force officials' efforts to influence the award of a $50 million contract, urging investigators to focus on the actions of key service leaders, The Associated Press has learned.

The chairman and the top Republican on the Senate Armed Services Committee have asked the Defense Department's inspector general to determine if there were any criminal or ethical violations or failures of leadership, particularly by senior Air Force officials.

Panel chairman Carl Levin of Michigan and Republican Sen. John McCain of Arizona, in a letter dated Monday and obtained by the AP on Thursday, said the investigation raised serious questions about the actions of senior Air Force officials.

Levin and McCain's letter does not name Gen. Michael Moseley, the Air Force chief of staff, who was linked to the scandal, though not directly blamed.

Additionally, another committee member, Sen. Claire McCaskill, D-Mo., spoke to Air Force Secretary Michael Wynne on Thursday to express her anger that Moseley was not reprimanded for his involvement in the contract issue.

Late last week, the Pentagon IG found that the 2005 contract to promote the Thunderbirds aerial stunt team was tainted by improper influence and preferential treatment. No criminal conduct was found.

In response, Air Force Secretary Michael Wynne took administrative action against Maj. Gen. Stephen M. Goldfein, who was the commander responsible for the Thunderbirds at the time, as well as two others, and referred action on two additional personnel to their commanders.

Moseley was not singled out for blame, but the investigation laid out a trail of communications from him and other Air Force leaders that eventually influenced the contract award. Included in that were friendly e-mails between Moseley and an executive in the company that won the bid.

"It is my sense that General Moseley's command authority has been compromised," McCaskill said in a letter to Wynne on Thursday.

She said that a letter sent by Wynne and Moseley warning senior Air Force officers to scrupulously avoid the appearance of favoring contractors should have been directed to Moseley instead of from him.

The letter, she said, "shows a degree of hypocrisy on General Moseley's behalf that is astonishing."

Wynne, in a statement last week, said he was deeply disappointed that the service's high standards were not followed, and said he was taking steps to ensure it did not happen again.