Floodwater overwhelmed a pump at Exxon Mobil Corp.'s Joliet, Illinois refinery, and the facility remains offline following the outage, Reuters reported.

The incident at the Midwestern plant knocked the refinery out of service, and it has yet to restart. Exxon Mobil has not disclosed a timeline for restoring operations at Joliet, and the company has offered no estimate of when crews will return the units to production.

The Joliet refinery sits on the Des Plaines River in Will County, southwest of Chicago, and forms part of the refining base that supplies gasoline and diesel to the Chicago-area market, one of the largest fuel-consuming regions in the U.S. Midwest. An extended outage at the plant tightens product supply in a market that traders watch closely through the Chicago benchmark differentials for refined products.

Reuters attributed the cause of the shutdown to floodwater that overwhelmed a pump at the facility. The report did not specify the date the flooding occurred, the extent of the damage to pumping or process equipment, or the current status of individual units at the site.

Exxon Mobil has not commented publicly on the restart schedule or on any impact to supply commitments. The company typically draws on its distribution network and inventories to cover customer requirements during outages of this kind.

The watch item: the restart date. Traders will track Chicago product differentials and any Exxon Mobil operational updates for the first sign of when Joliet returns to service.