The company has locked out union employees since May 1 of last year. It claims the facility has continued operating at full capacity despite being run by reduced staff of management and replacement workers.

The investigation is expected to take a few weeks to complete, according to National Labor Relations Board spokesperson Kayla Blado.

Local 13-243 of the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union will cease representing employees of the Beaumont plant if more than 50% of workers participating in the election vote to decertify. The election was organized after more than 30% of employees at the site signed a petition requesting it.

ExxonMobil locked out union workers last spring after the local distributed notice of a strike. The lockout is the basis for one of the union’s allegations of unfair labor practices. The company claims that all of its actions have been legal and that it initiated the lockout because a strike would have created safety risks for plant operations. The union counters that ExxonMobil began preparing for the lockout – through actions such as installing worker housing – before the strike was announced.

The refinery has crude oil throughput capacity of 369,000 barrels per day and makes petroleum products such as gasoline and low-sulfur diesel. It includes a lubricant blending and packaging plant that makes products such as Mobil 1 engine oils.

ExxonMobil has said it will end the lockout if the decertification vote passes, if employees decertify it through petition or if a new contract is approved. The company and union continued negotiating during the lockout but union members voted in October to reject a proposed contract.