A U.S. probe into the 13,000-barrel oil spill on TC Energy’s Keystone pipeline is expected to cut into crude flows ahead of the summer driving season.

A pipeline operator put a damaged section in Kansas back into service Dec. 29, a little more than three weeks after a spill dumped 14,000 bathtubs’ worth of crude oil into a rural creek.

TC Energy Corp. pushed back the full return of its Keystone oil pipeline by a week after a 14,000-barrel oil spill shut the critical conduit, according to people familiar with the matter.

The operator of a pipeline with the largest onshore crude oil spill in nine years has reopened all of it except for the stretch in Kansas and northern Oklahoma that includes the site of the rupture.

TC Energy’s efforts to restart a segment of its Keystone oil pipeline after a 14,000-barrel spill have been delayed by bad weather, according to people familiar with the matter.

The early December oil spill in Kansas means that TC Energy Corp.’s Keystone pipeline has now leaked more crude oil than any other conduit on U.S. land in the past 12 years.

An oil spill in a creek in northeastern Kansas this week is the largest for an onshore crude pipeline in more than nine years and by far the biggest in the history of the Keystone pipeline, according to federal data.

The Keystone oil pipeline system, a major conduit linking Canada to the U.S. Gulf Coast, was shut down after crude leaked into a creek in Kansas.