A statement posted on the company's website says the employee was pronounced dead at a hospital after being injured Sunday morning. The employee's name was not released.
The publicly traded company says it is working with authorities and will "complete a full investigation into the cause of the accident."
The company is one of several in Canada that supports the Keystone XL pipeline project that would carry oil from western Canada's tar sands to refineries on the Texas Gulf Coast. The project requires U.S. State Department approval because it crosses an international border.
The Obama administration last week said it was putting off indefinitely a decision on the project.
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