HOUSTON (Reuters) -Most of the units at BP Plc’s 435,000 barrel-per-day Whiting, Indiana, refinery were out of production on Thursday following a Wednesday night fire, said sources familiar with plant operations.

The company has said some units were shut by the electrical fire and those units would be restarting.

The timing of the restart had not been determined by midday Thursday, the sources said.

The fire affected utilities to multiple units at the refinery, and BP has called in most of the refinery’s employees to work on repairs and restarts, the sources said.

The incident at the Whiting refinery, the largest in the Midwest and BP’s largest anywhere in the world, drove up motor fuel prices in the Chicago market.

Chicago CBOB gasoline gained 30.5 cents per gallon, trading 3 cents above the futures benchmark on the New York Mercantile Exchange, market participants said.​

Chicago ultra-low sulfur diesel gained 17 cents, trading 20 cents above diesel futures.

(Reporting by Erwin Seba; Editing by Leslie Adler and Marguerita Choy)