The facility, which can produce up to 360,000 barrels per day, was hit by a power outage, sending the front-month U.S. crude spread surging to the widest in nearly four years.

Traders expect the Syncrude outage to tighten Canadian supplies and reduce crude flows to Cushing, Oklahoma, the delivery point of the U.S. crude futures contract.

Power and utilities have been restored to the site and Syncrude is conducting an assessment, which includes a return to service plan, Suncor spokeswoman Sneh Seetal said in an emailed statement.

Until the assessment is done it's too soon to provide an update to the restart timeline, Seetal said.

Syncrude is a joint venture majority owned by Suncor, with minority stakes held by Imperial Oil Ltd and others.

(Reporting by Devika Krishna Kumar in New York; Editing by Andrea Ricci)