The Pipeline and Hazardous Materials Safety Administration says TransCanada reported shutting down the approximately 2,100-mile pipeline, which moves about 500,000 barrels of crude a day from Alberta, Canada, to facilities in Illinois and Oklahoma.
Jeannie Layson, spokeswoman for PHMSA, says the possible safety issues were found on part of the pipeline that extends between Missouri and Illinois. Layson says in an email that an agency inspector has been sent to review the test results, observe repairs and follow any necessary safety activities.
She says TransCanada hasn't reported any leaks on the system, which passes through South Dakota.
TransCanada spokesman Grady Semmens says the pipeline was shut down Wednesday and is expected to restart Saturday.