This aerial photo shows spills from TransCanada Corp.'s Keystone pipeline, Friday, Nov. 17, 2017, that leaked an estimated 210,000 gallons of oil onto agricultural land in northeastern South Dakota, near Amherst, S.D., the company and state regulators said Thursday, but state officials don't believe the leak polluted any surface water bodies or drinking water systems. Crews shut down the pipeline Thursday morning and activated emergency response procedures after a drop in pressure was detected resulting from the leak south of a pump station in Marshall County, TransCanada said in a statement. The cause was being investigated. (DroneBase via AP)

This aerial photo shows spills from TransCanada Corp.'s Keystone pipeline, Friday, Nov. 17, 2017, that leaked an estimated 210,000 gallons of oil onto agricultural land in northeastern South Dakota, near Amherst, S.D., the company and state regulators said Thursday, but state officials don't believe the leak polluted any surface water bodies or drinking water systems. Crews shut down the pipeline Thursday morning and activated emergency response procedures after a drop in pressure was detected resulting from the leak south of a pump station in Marshall County, TransCanada said in a statement. The cause was being investigated. (DroneBase via AP)

AMHERST, S.D. (AP) — TransCanada Corp. says the company has sent additional crews and equipment to the site of a 210,000-gallon oil spill in South Dakota from its Keystone pipeline.

TransCanada said Saturday it is making progress in its investigation into the spill cause on farmland in Marshall County, near the North Dakota border, about 250 miles (402 kilometers) west of Minneapolis. But the company did not elaborate on the cause. The company says additional equipment and workers continue to be dispatched to the site.

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Company spokesman Terry Cunha said Sunday that about 150 people are now at the site. Cunha said a gravel road has been completed to handle heavy equipment.

Cunha said a drainage ditch near the leak was protected by a berm and not polluted by the spill. State officials earlier said they did not believe the spill has polluted any surface water bodies or drinking water systems. A drainage ditch is clearly visible in aerial footage taken by DroneBase on Friday.

Crews shut down the pipeline Thursday after discovering the leak.

TransCanada says the leak is under control and there is no significant environmental impact or threat to the public.

Nebraska regulators vote Monday on a proposed Keystone XL route, an expansion that also would be operated by TransCanada.