House Republicans on Thursday intensified their investigation into Solyndra, a California solar-panel manufacturer favored by the Obama administration that shut down this week.

Republicans on the Energy and Commerce Committee said they are seeking copies of all communications between the White House and Solyndra regarding a $535 million loan guarantee by the Energy Department. They are also seeking communications between the White House and investors in the company.

Solyndra was backed in part by capital from funds associated with George Kaiser, a Tulsa billionaire and Democratic fundraiser.

Energy and Commerce Committee Chairman Fred Upton (R-Mich.) and Cliff Stearns (R-Fla.), chairman of the oversight and investigations subcommittee, wrote to the White House, “We have learned from our investigation that White House officials monitored Solyndra’s application, and communicated with DOE and Office of Management and Budget (OMB) officials. Documents received by the Committee also show that DOE and OMB officials were aware of the White House’s interest in the Solyndra loan guarantee.”

Solyndra’s closing has also raised concerns about the status of tens of billions of dollars the Obama administration has invested in other renewable-energy companies.

Frank Rusco, a Government Accountability Office director who helped lead a review of the Solyndra loan and the Energy Department’s loan guarantee program, said the GAO remains “greatly concerned” by its 2010 finding that the agency agreed to back five companies with loans without properly assessing their risk of failure. The companies were not identified in the report, but the GAO has since acknowledged that Solyndra was one of them.

Solyndra, a signature project of President Obama’s initiative to help create clean-energy jobs, announced Wednesday that it was filing for bankruptcy protection and laying off 1,110 workers at its Bay Area plant. Obama and Energy Secretary Steven Chu had visited the plant, and Vice President Biden spoke at its groundbreaking via live video.

Solyndra was the first company to get a taxpayer-backed loan in the early weeks of the Obama administration, but there are more than 40 other clean-technology firms and projects the Energy Department has since backed or agreed to back with more than $38 billion in taxpayer funds.

Solar industry analyst Peter Lynch said other bad news might be looming in that clean-tech portfolio: “What Solyndra shows is that the administration wasn’t that good at assessing risk.”

What’s causing worry is that Solyndra was a company Obama had cited as a model of the industry he said he wanted to help develop in the United States. Taxpayers might end up on the hook for Solyndra’s $535 million loan, a default the Energy Department once said was highly unlikely.

The group of companies the department has backed have pledged to generate 66,000 jobs in 38 states. The department said Wednesday that the projects are meeting all benchmarks and are “on pace to create more than 60,000 jobs.”

Rusco said the department was premature in predicting jobs and suggesting that the success of 40 other clean-tech loan projects will more than offset what taxpayers lose on the Solyndra loan.

“This was the first loan guarantee,” Rusco said. “Most of the loans they’ve issued haven’t begun to produce things. We hope the value to society of all the other loans is greater than the loss here. But that remains to be seen.”

GAO auditors fear that similar defaults could happen with other projects, possibly including the other four it found weren’t properly vetted. The GAO last year uncovered the department’s rush to provide Solyndra its loan — less than 60 days after Chu was sworn in to the new administration — without completing required reviews.

The Energy Department’s inspector general criticized the agency this year for not maintaining e-mails discussing how loan-guarantee winners were selected.