Top U.S. refiner Valero Energy Corp said Tuesday a naphtha hydrotreater remained shut at its 87,400 barrel-per-day Ardmore, Oklahoma refinery after a Saturday night fire in the unit.

There was a small fire in a naphtha hydrotreater, it happened on Saturday night at about 11:30 p.m. local time; no injuries were reported in the fire which was quickly extinguished, said company spokesman Bill Day.

He said there was no estimate on the duration of the repair to naphtha hydrotreater, which has a capacity of 26,000 bpd.

The refinery's crude unit and gasoline-producing fluid catalytic cracker (FCC) were on circulation but not producing, Day noted.

That means that they are powered up and operating but not producing any fuel, the spokesman added. The crude unit and the FCC were not damaged, they have power. We are keeping them warm so they don't have to shut all the way down and then have to be brought back up. (Reporting by Haitham Haddadin; Editing by John Picinich)