TransCanada has restarted the Keystone oil pipeline that carries about 590,000 barrels of crude oil each day from Canada to facilities in the Midwest.
Oil began flowing again Monday afternoon. Company spokesman Shawn Howard says the system will be operated at a slightly reduced pressure for about 24 hours. Contractual delivery levels will resume in November.
TransCanada had shut down the pipeline Wednesday after tests showed possible safety issues.
The company had planned to restart the pipeline Saturday. Howard blamed logistical issues for the delay, saying bad weather complicated efforts to move equipment on site and made inspections take longer.
The potential problems were detected in a section of the line between Missouri and Illinois. Howard says there were no leaks and the pipeline system's integrity is sound.