HOUSTON (Reuters) – The fire-damaged hydrocracking unit at Motiva Enterprises’  235,000 barrel per day Convent, Louisiana, refinery was surrounded by high water on Friday from heavy rains overnight, sources familiar with plant operations said.

The other units at the refinery were not in danger of flooding from heavy rains that were continuing to fall in south Louisiana on Friday, the sources said.

The structure of the 45,000 bpd heavy oil hydrocracker, called the H-Oil unit, was heavily damaged in a blaze on Thursday and efforts to limit environmental damage from fighting the fire are contributing to the flooding around the HCU.

Rubber blocks were that were placed in storm drains on Thursday to prevent hydrocarbons from getting into the storm water system have become stuck, preventing drainage of the high water, the sources said.

The National Weather Service has issued a flash flood warning for south Louisiana on Friday, saying heavy rains since Wednesday have saturated the ground.

An initial assessment on Thursday of damage to the H-Oil unit’s structure was that repairs could take between one and four months, but a more detailed inspection and damage assessment cannot be conducted until the HCU cools down from the fire, said the sources, who were not authorized to speak publicly about the matter.

The detailed inspection could narrow or expand the time needed for repairs. The H-Oil unit’s reactors, where hydrogen is mixed with gas oil in motor fuel production, appeared to have little damage from the blaze in the initial assessment.

No injuries were reported from the blaze that lasted about four hours and all other units at the refinery remained in operation, Motiva said on Thursday.

Hydrocrackers use hydrogen under high pressure to produce motor fuels from gas oil produced by crude distillation units.

(Reporting by Erwin Seba; Editing by Chizu Nomiyama and Matthew Lewis)