WASHINGTON, Nov. 1 -Sen. Bernie Sanders (I-Vt.) today raised a series of new questions about the credibility of an environmental review of a controversial proposed oil pipeline from Canada to Texas.

Sanders had questioned “disturbing allegations” that TransCanada, the developer of the Keystone XL pipeline, screened applicants for an environmental impact study.

Instead of addressing the need for a new, impartial, and independent review, however, the State Department in a letter to Sanders downplayed the financial links between  Cardno Entrix, the company that did the study, and TransCanada.

In a follow-up letter today, Sanders said he remained “deeply troubled” about the environmental study. He asked the State Department for any contracts, agreements, memorandums of understanding, or other documents that describe the relationships between Cardno Entrix, TransCanada, and the State Department with respect to the proposed pipeline.

He also requested conflict of interest statements for all third-party contractors, including Cardno Entrix, regarding Keystone XL and records related to any meetings with representatives from the State Department, TransCanada, and Cardno Entrix.

“These documents should clarify definitively who the ‘client’ is in this case, how much control TransCanada has over the process, whether any improper meetings took place, and whether all parties have complied with their legal obligations in disclosing conflicts of interest,” Sanders said.

To read the senator’s letter, click here.