TC Energy says has not found cause of Keystone oil pipeline leak

Dec 11 (Reuters) - Canada's TC Energy said on Sunday it has not yet determined the cause of the Keystone oil pipeline leak last week in the United States, while also not giving a timeline as to when the pipeline will resume operation.

TC shut the pipeline after more than 14,000 barrels of crude oil spilled into a creek in Kansas on Wednesday, making it one of the largest U.S. crude spills in nearly a decade.

"Our teams continue to actively investigate the cause of the incident. We have not confirmed a timeline for re-start and will only resume service when it is safe to do so, and with the approval of the regulator," TC said in an update posted to its website.

The pipeline operator said that it has more than 250 people working on the leak, including third-party environmental specialists, adding that it is continuously monitoring air quality and presently there are no indications of adverse health or public concerns.

Crews are also preparing for rain forecast to begin on Monday, TC said.

The 622,000 barrel-per-day Keystone line is a critical artery shipping heavy Canadian crude from Alberta to refiners in the U.S. Midwest and the Gulf Coast.

Keystone's shutdown will hamper deliveries of Canadian crude both to the U.S. storage hub in Cushing, Oklahoma and to the Gulf, where it is processed by refiners or exported.