The company had shut down its 590,000 barrel-per-day Keystone pipeline, which links Alberta's oil sands to U.S. refineries, on Nov. 16 after a 5,000-barrel spill. It has not yet set an expected restart date for the pipeline, which is one of Canada's main crude export pipelines.

Additional excavation will be conducted beyond Sunday for soil remediation purposes, the Calgary-based company said, adding, it has about 170 personnel round-the-clock on the site engaged in clean-up activities.

Preliminary inspections of the damaged section will be completed on site by both TransCanada and U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) staff, then sent to Washington, D.C., for an investigation by the National Transportation Safety Board's Metallurgical Laboratory, the company said.

"As a safety precaution, TransCanada sampled one residential water well yesterday at a location about 1.5 miles from the site to alleviate any concerns — all test results were normal," TransCanada added.

(Reporting by Catherine Ngai in New York and Eileen Soreng in Bengaluru; Editing by Lisa Shumaker)