The refining unit of Citgo located in Lemont, Illinois was shutdown temporarily for repairs, operators said Thursday. Citgo is a subsidiary of state-run oil holding Petróleos de Venezuela (Pdvsa) based in the United States.

"There was a fault in the crude oil distillation unit (CDU)," an operator said, adding that there was a 24-hour delay to reopen the facility, Reuters reported.

The refinery has a processing capacity of 167,000 bpd.

The company spokesman was not available for comments.