LyondellBasell Industries was returning its 263,776 barrel per day Houston refinery to normal operations on Wednesday, one day after a power interruption on a unit cut production in half, sources familiar with plant operations said.

A Lyondell spokeswoman on Wednesday declined to discuss operations at the refinery.

The sources said production at the refinery had been at full capacity when the sulfur recovery unit lost power on Tuesday afternoon. Refinery production was cut, amid worker evacuations and orders to shelter in place, to about half capacity following the power interruption.

Because of the quick restart of the SRU, the refinery is expected to return to full production within a few days, the sources said.

Last month, the company said the refinery’s production averaged 73 percent of capacity during the second quarter of 2016 as Lyondell performed extensive repairs to a coking unit damaged in an April 8 fire. It added the refinery was not able to run at full production until the coker restarted on July 15.

Flaring from the refinery lasted for about eight hours beginning at 2 p.m. CDT (1900 GMT) on Tuesday, the sources familiar with the plant’s operation said.

Lyondell said on Tuesday that air monitoring did not detect unsafe levels of pollutants.

The Houston Ship Channel was shut for about 20 minutes on Tuesday afternoon so the crew of a ship on the waterway north of the Lyondell refinery would not be exposed to a hydrogen sulfide release from the refinery, the U.S. Coast Guard said.

A sulfur recovery unit extracts sulfur from hydrogen sulfide removed from motor fuel feed stocks in compliance with U.S. environmental rules.