By Roberta Rampton

WASHINGTON (Reuters) - Republicans probing a $535 million federal loan guarantee to bankrupt Solyndra said on Wednesday they will keep pressing the White House to release more internal emails about the failed solar maker.

The White House told lawmakers on Friday that it would not release any more documents for the investigation, saying more documents would be released by the Energy and Treasury Departments, along with the Office of Management of Budget.

Republicans, however, say the White House still holds material they want to see.

"The internal communications regarding Solyndra which we have requested from the White House are not in the possession of the other agencies," said Fred Upton and Cliff Stearns, the Republicans on the House Energy and Commerce committee who are leading the investigation, in a letter to top White House lawyer Kathryn Ruemmler.

Solyndra used the 2009 loan guarantee to build a solar panel plant under a program designed to spur jobs in renewable energy. But the project became a embarrassment for the Obama administration after it filed for bankruptcy on September 6 and was raided by the FBI.

Upton and Stearns first asked for the internal emails on Oct 5. Ruemmler had told them that the request encroached on "longstanding and significant institutional executive branch confidentiality interests.

The lawmakers called that claim "vague" and said the committee is entitled to the documents "unless the President actually asserts a valid claim of executive privilege."

Republicans have so far amassed more than 70,000 pages of documents in their investigation.

They have questioned whether private investors in Solyndra who had contributed to President Barack Obama's election campaign had influence over decisions on the loan.

"There is nothing in the documents ... that the White House intervened in the Solyndra loan guarantee to benefit a campaign contributor," Ruemmler told the lawmakers last week.

Obama has said government decisions on Solyndra were based on the merits of the project.

(Editing by Mohammad Zargham)