Two Exxon Mobil refineries were damaged by Hurricane Harvey, causing the release of chemical pollutants over parts of Houston.

Exxon on Tuesday filed a report with Texas environmental regulators that said a roof at its refining facility in Baytown "partially sank" because of heavy rain. The Baytown refinery is the second-largest in the country.

Exxon also said in the filing that Harvey damaged its Beaumont petrochemical refinery.

The damage affected a sulfur thermal oxidizer, equipment that captures and burns sulfur dioxide. As a result, the plant released 1,312.84 pounds of sulfur dioxide into the atmosphere.

Exxon said it was taking action to "minimize emissions" from the release of chemicals at the damaged plants.

In a statement to reporters, Exxon would not immediately detail the extent of the damage or the emissions fallout, saying it plans to assess the impact "once it is safe to do so."

Harvey has temporarily knocked offline about 15 percent of U.S. refining capacity, including the two Exxon refineries.