A major pipeline transporting crude oil from Canada to the US Gulf Coast has been shut down after a 3500-barrel leak in North Dakota.

An oil spill in North Dakota on Tuesday morning shut down some 2,700-miles of the Keystone oil pipeline and halted the flow of millions of gallons of crude oil from Canada to refineries in the U.S.

The operator of the Keystone oil pipeline brought the conduit back into service, putting an end to a weeklong outage caused by an estimated 3,500-barrel spill in rural North Dakota.

The 2,689-mile Keystone Pipeline carries crude oil from Alberta, Canada, to refineries in Illinois, Oklahoma and Texas.