Oil refineries in the Houston area damaged by Hurricane Harvey may have accidentally released millions of pounds of contaminants into the air, according to news reports.

Chevron Phillips Chemical told the Texas Commission on Environmental Quality that it may have released more than 745,000 pounds of airborne pollutants as it shut down its Cedar Bayou Plant in Baytown, Texas. Oil refineries and other facilities are required to file emissions reports estimating the amount of contaminants released into the air as soon as an event occurs.

An estimated 300,000 pounds of contaminants were reportedly released, along with gasoline, when flooding submerged 128 tanks holding petroleum products at the Pasadena Terminal.

Approximately 12,000 pounds of contaminants may have been emitted by two Houston-area ExxonMobil refineries damaged by the storm and subsequent flooding.

That commission is unable to confirm the exact amount of releases at this time because air- quality monitoring stations throughout the area were shut down prior to Harvey's landfall.