This story was updated at 3:30 p.m. EST.

On the first anniversary of the start of a probe into the Energy Department's loan guarantee to Solyndra, House Energy and Commerce Committee Republicans today are venturing further down the rabbit hole, demanding the release of new documents about Energy Secretary Steven Chu's involvement in a separate $1.4 billion loan guarantee deal.

Republicans said in a letter to Chu today they are concerned that a loan guarantee granted to the solar generation company Prologis last year was advanced in part to benefit the struggling Solyndra solar tube manufacturing company, which went bankrupt in August 2011 after receiving more than half a billion dollars in DOE loan guarantee funding.

DOE guaranteed the loan to Prologis for its Project Amp initiative, which includes the installation of 752 megawatts of photovoltaic solar panels on 750 rooftops across the country that are owned and managed by Prologis. DOE estimated the project would create 1,000 jobs over the next four years and cut some 580,000 tons of carbon pollution annually while feeding power to utilities and other power purchasers. The loan was finalized by DOE in September 2011.

Citing documents uncovered in the course of their Solyndra investigation, Energy and Commerce Chairman Fred Upton (R-Mich.) and his lead investigator, Rep. Cliff Stearns (R-Fla.), charged today that Chu became personally involved in Project Amp because Solyndra products were at one point considered for use in the rooftop project. The lawmakers also questioned whether the Prologis deal was a factor in potential loan restructuring talks between DOE and Solyndra in August 2011.

DOE restructured the Solyndra loan once in late 2010, but a second restructuring was not approved late last summer. Solyndra declared bankruptcy soon after.

"We have questions about Solyndra's involvement in Project Amp, and what role Solyndra's involvement played in DOE's decision to issue a conditional commitment to Prologis for the project," Upton and Stearns wrote. "Based on our review of documents produced to the committee, it appears that Solyndra's involvement in Project Amp was a significant factor both in the negotiations between DOE and Solyndra relating to a possible second restructuring of the loan guarantee in August 2011 and in the closing of the Project Amp loan guarantee."

DOE said today that Solyndra and Prologis had parted ways well before the department finalized its loan for Project Amp and that Chu's involvement in the deal stemmed from a disagreement that arose between DOE and other agencies about the number of megawatts the project should support and how long the installation period should take.

"Project Amp represents a transformational new approach to financing and operating solar panels and has been supported by some of the most prominent companies in the world, including Merrill Lynch, Bank of America and NRG Energy," said DOE spokesman Damien LaVera. "As has consistently been the case in the course of this committee's yearlong political investigation, critics of our effort to support innovative, job-creating clean energy projects will say anything to distort the record."

Click here to read the letter.