Tesoro Corp. restarted a sulfur recovery unit at its refinery in Kapolei after an unscheduled shutdown Tuesday.

Normal operations resumed at 5:45 p.m. after about three hours of flaring, Mike Marcy, a company spokesman, said in an e- mail. No injuries were reported, the proper authorities were notified and the incident didn’t affect production or operations, Marcy said.

A filing with the National Response Center said about 3,000 pounds of sulfur dioxide were released to the flare.

U.S. plants must notify the response center if they release hazardous substances in excess of permitted quantities, according to the Comprehensive Environmental Response, Compensation and Liability Act, commonly known as Superfund.