DENVER: Exxon Mobil on Monday said its Baytown, Texas, refinery continued to operate at reduced rates following a fire on Dec. 23, and that the unit involved remained shut down.

The company has not yet determined the cause of the fire, but said it was continuing to empty the unit so it could safely enter the facility and assess what impact it would have on production.

A filing with the Texas Commission on Environmental Quality said the fire occurred at the facility’s Hydro Desulfurization Unit 1.

Exxon’s Baytown facility is home to a chemical plant, an olefins plant and the country’s fourth-biggest oil refinery, with capacity to process 560,500 barrels per day of crude.

Four workers were hospitalized as a result of the incident, two of whom were confirmed to have been released from the hospital. Exxon declined to provide an update on the status of the other injured workers.

A group of nearby homeowners who said their houses were destroyed by the fire have filed a lawsuit against Exxon. The suit asks a Texas court to restrain the company from altering, destroying or modifying evidence relevant to the explosion until the plaintiffs’ counsel can conduct its own inspection.

The suit says Texas officials have condemned the damaged homes. Exxon did not immediately respond to a request for comment on the lawsuit.