U.S. Sens. Ron Wyden, D-Ore., Patrick Leahy, D-Vt., and Bernard Sanders, Ind.-Vt., said in a letter to the State Department that its decision to hire Texas consulting company Cardno Entrix at the suggestion of Canadian pipeline company TransCanada is suspicious.
"We find it inappropriate that a contractor with financial ties to TransCanada, which publicly promotes itself by identifying TransCanada as a 'major client,' was selected to conduct what is intended to be an objective government review (of the pipeline)," the letter read.
Ties between Cardno Entrix and TransCanada were revealed by The New York Times. Wendy Nassmacher, a spokeswoman for the State Department, told the newspaper that the department has "received the letters and we are currently reviewing them."
The State Department needs to approve the pipeline because it crosses international boundaries. U.S. Secretary of State Hillary Clinton was criticized for her ties to Paul Elliot, who worked on Clinton's 2008 presidential campaign team and now works as a lobbyist for TransCanada.
Critics of the pipeline complain the project isn't worth the environmental risk though its supporters said it's good for regional energy security.
The State Department, which said it didn't anticipate major environmental problems with the project, is expected to make a decision by the end of the year.
A recent editorial by The New York Times expressed direct opposition to Keystone XL.