Production at LyondellBasell's 270,000 barrel per day (bpd) Houston refinery was "down to very low rates" with both crude distillation units shut on Monday, a company spokesman said.

One of the CDUs was shut by a Monday afternoon fire and the second CDU was preparing to restart on Tuesday after being shut for unplanned repairs, said Lyondell spokesman David Harpole.

"We would be down to very low rates," Harpole said.

Crude distillation units do the initial refining of crude oil coming into a refinery. Harpole said it was unknown how long it would take the CDU to return full to production after it begins the restart process. The refinery continues to make gasoline from feedstocks on hand, he said. No injuries were reported due to the fire that broke out at about 2:30 p.m. local time at the refinery located along the Houston Ship Channel, Harpole said.

The fire was extinguished in about an hour. All employees were accounted for. The fire generated heavy black smoke because the product in the crude unit at the time the fire broke out was of a grade between gunky residual crude and diesel, he said.

Local residents were told to remain inside and shut down their air conditioning units due to the smoke. It was too early to tell what damage the crude unit had sustained and how long it would take to return it to production, he said. The Houston refinery is one of two owned by LyondellBasell, which emerged from bankruptcy on April 30, a 16-month struggle that saw it shed $19 billion in debt.