OnEarth.org, a website of the Natural Resources Defense Council, published documents that indicate Rice owns at least $300,000 worth of stock in TransCanada, the company planning Keystone XL.
Rice is reportedly being considered to replace Hillary Clinton as secretary of state. The U.S. State Department is vetting the proposal for the Keystone XL oil pipeline because it would cross the U.S.-Canadian border.
A domestic leg of the pipeline is under construction in the southern United States.
Bill McKibben, founder of the Tar Sands Action network, was quoted as saying the State Department has been "rife with collusion with the Canadian pipeline builders."
Clinton sparked controversy in 2010 when she said the United States was either going to get "dirty oil" from the Middle East or "dirty oil" from Canada.
OnEarth.org say the Rice family owns more than $1 million in stock in four of Canada's top oil-producing companies.
NRDC director of international programs Susan Casey-Lefkowitz told Bloomberg News her organization expects Rice to sell her controversial holdings should she be nominated and approved to become secretary of state.
"U.S. law actually requires a pretty rigorous conflict-of-interest check and we would expect that she would be getting rid of holdings that are in conflict with a decision on a project like the Keystone XL tar sands pipeline," she said.
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