(Updates to state that TransCanada has restarted the pipeline)
By Catherine Ngai and Ethan Lou
April 10 (Reuters) - TransCanada Corp on Sunday said it had restarted the 590,000- barrel-per-day Keystone crude pipeline at reduced pressure after it received American authorization to do so.
The Canadian energy company said the U.S. Pipeline and Hazardous Materials Safety Administration approved the return to service plan for a controlled start Saturday evening.
The pipeline, which delivers light and heavy crude from Hardisty, Alberta, to Cushing, Oklahoma, and Illinois, was shut on April 2 after a potential leak was discovered in South Dakota.
"As part of the return-to-service plan approved by PHMSA, TransCanada is operating the pipeline at reduced pressure," the company said in a statement.
In an e-mailed statement to media on Friday, the company said it identified the leak near its Freeman pump station in Hutchinson County, South Dakota.
The company also said it will conduct aerial patrols and visual inspections during the restart. (Reporting by Ethan Lou in Toronto; Editing by Nick Zieminski and Alan Crosby)