Congressional investigators are probing potential cronyism in a pair of federal green energy programs, including the Energy Department loan program that guaranteed a $535 million loan to now-bankrupt solar company Solyndra.

In a letter to Interior Secretary Ken Salazar sent on Tuesday, embedded below, Sen. Jeff Sessions (R-AL), chairman of the Budget Committee, and Rep. Darrell Issa (R-CA), chairman of the House Oversight Committee, ask for information on federal support for six different companies: Abengoa Solar, BrightSource Energy, First Solar, Nevada Geothermal, NextEra Energy Resources, and SolarReserve.

Sessions initially requested the information last year, but DOI has yet to respond. The letter calls the department’s silence “unacceptable.”

Session and Issa are wondering whether DOI fast-tracked regulatory approval for a spate of green energy projects with notable political connections and ties to the Obama administration.

According to a Republican aide on the Senate Budget Committee, Salazar’s department has created a two-tiered system for energy companies looking to secure federal support. “Politically favored, and often connected, renewable energy plans [receive] less rigorous review than traditional energy projects,” the aide asserted.

Each of the companies mentioned in the letter has a significant political footprint. For instance, former BrightSource CEO John Bryson is now Commerce Secretary. Senate Majority Leader Harry Reid (D-NV) was instrumental in securing federal backing for Nevada Geothermal, even pressuring Interior to fast-track the company’s loan guarantee approval process.

Steve Black, a senior official at DOI, leads the Renewable Energy Policy Group, which also includes NextEra lobbyist Manal Yamout. Black and Yamout are reportedly in a romantic relationship.

The lead lobbyist for First Solar, vice president of government relations Kathleen Weiss, has had numerous meetings at the White House, according to visitor logs. She has met with senior White House official Valerie Jarrett, Deputy Assistant to the President for Energy and Climate Change Heather Zichal, among others.

While Interior has yet to respond to the request for information on these and other companies, the appearance of political favoritism in DOI’s review of green energy projects fits with a pattern of cronyism in the administration’s “green” initiatives.

Here is the full text of the letter to Salazar:

Sessions Issa Letter to Salazar