Phillips 66's 356,500 barrel-per-day Wood River refinery is undergoing a turnaround, research company IIR Energy said on Thursday.

The refinery, in Roxana, Illinois, began maintenance activities last week, IIR said.

Ongoing maintenance work at the refinery's 170,000-bpd crude distillation unit, 50,000-bpd vacuum flasher, 42,000-bpd catalytic cracker unit, and associated gas plant units is expected to continue until late April.

The Wood River refinery produces transportation fuels including gasoline, diesel and aviation fuel.

A Phillips 66 spokesperson declined to comment on refinery operations.