WASHINGTON (AP) — Hillary Rodham Clinton's personal lawyer has told a Senate committee that emails and all other data stored on her computer server were erased before the device was turned over to federal authorities.

In a letter sent last week to Sen. Ron Johnson, R-Wis., the chairman of the Senate Homeland Security Committee, attorney David Kendall said the server was transferred to the FBI on Aug. 12 by Platte River Networks, a Denver firm hired by Clinton to oversee the device. The Senate committee made Kendall's letter public on Wednesday. In exchanges with reporters earlier this week, Clinton said she was not aware if the data on her server was erased.

Confirmation that the server was wiped clean came amid mounting confusion over how sensitive some of the Clinton emails were and how much of their contents should have been released. Clinton aides said at least two emails that might have triggered the federal inquiry were not marked secret at the time. But a Republican senator said Wednesday that U.S. inspector generals for the State Department and the intelligence community were told by some of the agency's freedom of information specialists that department lawyers released some Clinton materials to the public over their objections.

Federal investigators, prompted by a request from the inspector general for the State Department, requested custody of the server to learn whether the data stored on it was secure. NBC News has reported that an FBI team is now examining the server. Forensics experts told The Associated Press this week that some emails and other data may still be extracted from servers even after they are supposedly expunged.

Separately, John Podesta, Clinton's campaign chairman, told reporters Wednesday in Columbia, South Carolina, that, to his knowledge, no other copy had been made of the server's contents other than those her lawyers turned over to the FBI.

As campaign officials answered questions, one of Clinton's rivals said the email issue has become a distraction for the Democratic Party.

"I think that it's a huge distraction from what we should be talking about as a party," former Maryland Gov. Martin O'Malley told reporters in Nevada.

Instead, he said more debates should be held among the candidates to address raising the minimum wage, repairing the country's infrastructure and other issues. "Until we do, our party's label is going to be the latest news du jour about emails and email servers and what Secretary Clinton knew and when she knew it."

O'Malley said some people in the Democratic National Committee are "circling the wagons."

Kendall, Clinton's long-time personal lawyer, said in his letter to the committee that both he and another lawyer at his firm were given security clearances by the State Department to handle a thumb drive that contained about 3,000 emails later turned over to the agency. Kendall said the thumb drive was stored in a safe provided in July by the State Department. Kendall did not say when he was given his clearance from State. The GOP-dominated Senate Judiciary Committee has asked Kendall if he had any access to Clinton's emails before he was given his security clearance.

Republican senators on both committees are pressing to see whether any emails sent or received by Clinton on the private server while she was secretary of state contained any secret information that should have been only exchanged on secured, encrypted government communications portals. An inspector general for the State Department said recently that several emails sent to Clinton did include such classified material — signaling that the transmission of those emails may have risked violating government guidelines for the handling of classified material.

Clinton campaign officials on Wednesday sought to show that the information contained in the emails that she received did not risk spillage of classified data at the time they were sent to her. During a conference call, campaign aides pointed to a Fox News report that at least two of the emails that prompted the inspector general's referral may have contained sensitive information but were not marked "classified" at the time they were sent to Clinton by aides.

Campaign spokesman Brian Fallon noted that the two emails were sent to Clinton from career diplomats, not political appointees, and that they "did not have information marked 'classified' or any classified documents attached to them."

Information in one of the documents, a 2012 email to Clinton about arrests in Libya, was later classified as secret by the FBI, but then released with redactions this year by the State Department, highlighting a dispute between the two agencies over whether the material should have been made public. A second email from 2011 was also released in full but reportedly contained classified military information.

"All this goes to show that when it comes to classified information, not all standards are black and white," Fallon said.

There are disputes even within the State Department, said Senate Judiciary Chairman Sen. Charles Grassley, R-Iowa. In a letter sent Wednesday to Secretary of State John Kerry, Grassley said several State FOIA examiners told inspectors general that several lawyers from the State Department Office of the Legal Advisor fully cleared some Clinton emails for public release despite recommendations that several passages needed to be censored for national security reasons.

"This dispute may have already contributed to at least one classified email being inappropriately released to the public," Grassley said. He also questioned whether some State Department lawyers may have had potential conflicts of interest.

State Department spokesman Alec Gerlach said: "The law is what governs redactions and upgrades. We are making appropriate redactions — following the standards laid out under FOIA for redactions as well as the rules governing classification as defined" by presidential orders.

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Associated Press Writer Meg Kinnard in Columbia contributed to this report.