Keystone pipeline developer TransCanada Corp. has begun loading oil into the southern leg of the project, which runs from Oklahoma to the Texas coast, The Houston Chronicle reports.
"The pipeline owner will need to fill the newly constructed line before it can begin delivering oil to refineries along the Gulf Coast, including those in Houston," the Chronicle reports.
"TransCanada plans to fill the new pipeline system with about 3 million barrels of oil in the coming weeks," the paper reports.
But the controversial northern leg of the project remains in limbo.
The White House is weighing whether to grant a permit for the pipeline segment that would bring crude from Alberta's oil sands across the border to link up with the southern portion.
Environmental groups battling the project made their latest case to the State Department on Monday.