Tribal issues latest Keystone XL concern 18 (UPI) -- Canadian pipeline company TransCanada said it was working with American Indian tribes on plans to build the Keystone XL pipeline through Oklahoma. TransCanada aims to build its Keystone XL pipeline to carry crude oil derived from oil sands operations in Alberta. Indian tribes in Oklahoma said they were concerned about the sovereign rights of their land. George Thurman, leader of the Sac and Fox tribal nations, expressed concern about interference with sacred archeological sites along the possible pipeline route. "There are mass graves where people were buried after dying of smallpox," Thurman told The Washington Post. There could be another buried out there. Lou Thompson, the company's tribal liaison, said the pipeline wouldn't cross tribal lands. He added that his company wasn't legally obligated to work with American Indian communities, but did so because it was the "neighborly thing to do." A lawyer working with tribes in South Dakota told the Post the laws presented a "tough question to answer." Environmental groups in Nebraska challenged state laws regarding pipeline jurisdiction. Texas landowners have challenged eminent-domain laws regarding the project. TransCanada already started construction on the Gulf Coast Project, the U.S.-leg of the pipeline.