Pemex's Deer Park oil refinery near Houston discharged 43,500 pounds of highly toxic hydrogen sulfide gas over more than seven hours in a deadly incident earlier this week, according to the Mexican state-owned company's disclosure to a Texas regulator.

The Pemex refinery chemical leak killed 2, injured dozens and forced shelter-in-place orders in Deer Park and Pasadena. They have since been lifted.

At least two workers at a Houston-area oil refinery were killed when hydrogen sulfide leaked at the plant, setting off urgent warnings for nearby residents to stay indoors before authorities determined the public wasn't in danger.