A letter from Sen. Bernie Sanders (I-VT) and Rep. Steve Cohen (D-TN) appears to have triggered what thousands of protesters could not: a serious re-examining of the deal to secure the Keystone XL tar sands pipeline.

"We are disturbed by reports, such as those in The New York Times on October 7, 2011, that the State Department allowed TransCanada, the pipeline developer, to screen applicants to conduct the [environmental impact study] mandated by federal law," their letter reads, going on to worry that the process may have been corrupted by a "conflict of interest."

Responding to the request for an investigation into the State Dept. handling of the deal, the Office of Inspector General said it would oblige.

"The primary objective of the review is to determine to what extent the Department and all other parties involved complied with Federal laws and regulations relating to the Keystone XL pipeline permit process," inspector Harold W. Geisel wrote (PDF).

The investigation would likely look at emails released earlier this year by environmental advocacy group Friends of the Earth, which claimed that documents obtained through Freedom of Information Act (FOIA) requests showed improper relationships between TransCanada lobbyists and State Dept. employees. Officials have since denied "complicity" in helping to secure the deal, which the State Dept. claimed would have minimal environmental impact.

Environmentalists disagree with this position, pointing to spill after spill of toxic crude oil. One striking example often cited by activists was the rupture of an Exxon Mobile pipeline earlier this year, which contaminated Yellowstone River. That pipeline was carrying crude oil from tar sands, which is known to be heavier and even more toxic than other types of oil.

Over 10,000 people gathered at a protest outside the White House on Sunday to protest the pipeline, which would move oil pulled from Canada's tar sands 1,700 miles south, across the whole United States, to refineries on the Texas Gulf coast.

Chanting "Yes we can, stop the pipeline," the protesters succeeded in literally surrounding the White House with a two-mile long human chain.

President Barack Obama, who was swept to power in part on promises to help ween America off its addiction to oil-based energy sources, was not present to witness the protest.

So far, hundreds of people have been arrested in voluntary acts of civil disobedience while protesting against the pipeline. The arrestees include Dr. James Hansen, NASA's top climate scientist, who insisted that if President Obama allows the pipeline to go through "it will confirm that the President was just green-washing all along, like the other well-oiled coal-fired politicians, with no real intention of solving the addiction."

Tar Sands Action, one of the main groups leading the protests against the pipeline, applauded the inspector general for announcing the probe, but cautioned that examining the deal's process was merely secondary to their real concerns.

"[W]hile we’ve been dismayed by the corrupt conduct of the state department, our real problem has from the start been the fact that these tar sands are the second largest pool of carbon on earth," a prepared statement reads. "Since the State Department didn’t even bother to study that global warming question, the only real answer is to send this back for a whole new review — or, better yet, for the President to simply back up his campaign promises and deny the permit outright."

"We believe that given the importance of this project and the controversy regarding the State Department's process to-date, a thorough investigation covering the questions we have raised, and any other possible violations of federal law or improper conduct related to the State Department EIS and NID process for the Keystone XL pipeline, is warranted," Sanders' letter concludes.

This video examining Sunday's Tar Sands XL protest in Washington, D.C. was published by The Huffington Post.

Photo: Flickr user Tar Sands Action.