CP spokesman Ed Greenberg says the rail line was reopened Thursday night after full track repairs and mandatory inspections were finished.
About 20 freight cars — including two that were carrying light sweet crude oil — went off the tracks Wednesday morning near White River, about halfway between Thunder Bay and Sault Ste. Marie.
CP (TSX:CP) said in a statement that while it initially thought only four barrels of oil had escaped the toppled cars, it later discovered that 100 times that amount — about 400 barrels — had spilled.
Greenberg says crews had quickly contained a leak from one of the cars but didn't realize oil had spilled from the other until much later Wednesday, because the spill was under the snow and migrated "a short distance."
Investigators with the Transportation Safety Board and the provincial Ministry of the Environment have been sent to the site.
Crews continued to work on cleaning up the spill Friday, and Greenberg says steps such as building a berm have been taken to contain the leak. All the oil will be removed during the cleanup, he said.
"CP takes these incidents seriously," he said in a statement, adding samples of soil and ground water were being taken around and below the site.
"There is no indication from any of the sampling sites that the product has migrated beyond the containment berms," he said.
Note to readers: This is a corrected story. An earlier version said the oil leak was 10 times more than first announced.