As is the case with many industrial accidents like the Beaumont plant explosion, multiple parties may be found to be responsible for an accident. In this case, the petrochemical plant is owned by ExxonMobil, which makes that mammoth company a key party likely to be deemed responsible for the accident.
With that said, culpability is not likely to begin and end with ExxonMobil. There were employees on site, specifically involved in the maintenance process where the explosion occurred, that work for a trio of other companies. These companies are KT Maintenance, Signature Industrial Services, and Brock Services, LLC. One or all of these enterprises might ultimately be deemed to have contributed to the explosion that caused injuries to a dozen workers on site.