Exxon Mobil Corp was preparing on Tuesday to return to production the second-largest crude distillation unit at the 560,500 barrel per day (bpd) Baytown, Texas, refinery later this week, said sources familiar with plant operations.

The unit was taken out of production on Monday due to malfunction, the sources said.

Exxon spokesman Todd Spitler said unplanned maintenance was continuing at the Baytown refinery with minimal impact to production. He would not say whether the company planned to restart the unit.