The US Chemical Safety and Hazard Investigation Board (CSB) and Occupational Safety and Health Administration (OSHA) are both launching independent investigations into this week's fatal accident at Pemex's 312,500 b/d Deer Park, Texas, refinery.
A hydrogen sulfide (H2S) release that killed two workers and injured dozens more occurred on Thursday evening at the plant located near Houston. It also led to shelter-in-place orders for surrounding communities, which have since been lifted.
The CSB will investigate the causes of the fatal release, the agency said Friday. The CSB is responsible for investigating industrial accidents in the US, such as the deadly 2022 explosion at BP's Toledo refinery in Ohio and a probe into operations at Marathon's Martinez renewable diesel plant after several fires earlier this year.
A representative for CSB was not immediately available for comment.
OSHA — charged with enforcing compliance with federal workplace safety laws — is also investigating the incident, and has "up to six months" to complete the investigation, according to an OSHA representative.
OSHA would not stop company operations during the duration of the investigation, but "could not speak for other agencies at the site," an OSHA official told Argus.
The Harris County Sheriff's department has also opened an investigation into the incident.
The release occurred as workers began planned maintenance on a unit. An H2S leak was detected, resulting in several units being shut down as staff sought to secure the leak.
The Deer Park refinery had previously been damaged in a February 2023 fire, resulting in two weeks of repairs. A slew of accidents at Deer Park and several other Mexican state-owned Pemex's refineries in part led Fitch Ratings to downgrade Pemex's credit rating in July 2023.
