WASHINGTON - Hillary Clinton's run for the White House is facing new questions focused on undisclosed foreign donations to Clinton Health Access Initiative (CHAI). CHAI, based in Boston, is one of the largest Clinton charities.

In 2013 alone, foreign countries donated at least $54 million to CHAI to help fight HIV/AIDS and other illnesses. But CHAI didn't inform the State Department -- that year or any year -- when Clinton was Secretary. The lack of disclosure was in spite of a 2008 memo of understanding stating that the Clinton "foundation will share such countries" with a State Department "ethics official for review."

"One has the impression that they didn't take this commitment seriously," said Louisiana Republican Sen. David Vitter.

Vitter grilled Clinton about potential conflicts of interest at her 2009 confirmation hearing when she promised that, "all contributors would be disclosed."

But in addition to CHAI, the foundation also acknowledged this week it did not disclose 1,100 mostly foreign donors to the Clinton-Giustra Enterprise Partnership. Officials for the Canada-based charity say revealing those names would violate Canadian laws.

Candidate Clinton has avoided the issue while foundation officials say they are acting quickly to remedy past mistakes. The Clinton campaign argues that there is no proof that Secretary Clinton was influenced in any way by the foreign donations.

"In this case emails were destroyed. In this case certain contributions were never disclosed," said Vitter. "And so it's hard to prove or disprove anything when that's the case."

A State Department spokesperson said Thursday the department would have liked to review those foreign donations. And Bernie Sanders, Clinton's new Democratic challenger, said the foundation donations are a fair campaign issue.