The State Department’s inspector general said Monday that he will conduct a special review of the department’s analysis of TransCanada’s proposed Keystone XL pipeline.

Howard W. Geisel said he will examine the department’s handling of its environmental impact statement and its process for determining whether the pipeline would be in the national interest, both part of the permitting process that President Obama delegated to the State Department.

The inquiry is likely to scrutinize the use of Cardno Entrix, which also has worked extensively for TransCanada, to draw up State’s environmental impact statement. Geisel said he was responding to a request for an inquiry made by Sen. Bernard Sanders (I-Vt.), Rep. Steve Cohen (D-Tenn.), two other senators and 10 other House members, who focused on that issue.

Opponents of the pipeline used the announcement as an opportunity to press anew for the Obama administration to reject the pipeline, which would carry heavy crude from Canada’s oil sands region in Alberta all the way to Texas refineries along the Gulf of Mexico coast. Environmentalists object because the extraction and use of Canada’s oil sands emit 5 percent to 15 percent more greenhouse gases than the average barrel of crude used in the United States.

“Our real problem has from the start been the fact that these tar sands are the second largest pool of carbon on earth,” said activist and author Bill McKibben, who helped organize anti-pipeline protests outside the White House. “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.”

Friends of the Earth President Erich Pica, whose organization used the Freedom of Information Act to obtain e-mails between a TransCanada lobbyist and officials at State, called the pipeline review “a sham, corrupted by bias, lobbyist influence and conflicts of interest. It should be obvious to the White House that it would be wholly inappropriate to continue moving forward with this rigged process.”

The State Department had no comment on the inspector general’s action Monday. State officials have in the past said the department is committed to a fair and thorough process that includes listening to opinions from both sides.

TransCanada spokesman Terry Cunha said that “at TransCanada, we conduct ourselves with integrity and in an open and transparent manner. We are certain that the conclusion of this review will reflect that.”