Local labor board officials upheld the results of a union election at a Portillo’s food preparation facility in suburban Addison after a series of challenges by the company.

Food preparation staff in Addison voted 28 to 20 to unionize with the International Association of Bridge, Structural, Ornamental and Reinforcing Iron Workers in April. Days later, Portillo’s asked the labor board to set the results aside, claiming the union made illegal promises to workers in the run-up to the election, including that union representatives told workers they could qualify for green cards or citizenship if they voted “yes.”

Arise Chicago, a Chicago-based workers’ center that has been organizing with the Portillo’s staff since 2021, has described the company’s claims as “baseless.”

This summer, labor board officials issued a report recommending overruling the company’s objections. Portillo’s subsequently appealed that decision. On Monday, the labor board’s regional director in Chicago, Angie Cowan Hamada, ruled again in favor of the union.

“Overall, the testimony from employee witnesses shows that [the Iron Workers and Arise] did not promise to obtain work permits for employees in exchange for signed authorization cards or Union votes,” Cowan Hamada wrote in her decision certifying the workers’ bargaining unit.

Portillo’s could request a review of the latest decision and has until Jan. 3 to do so. The company did not immediately respond to a request for comment Wednesday.

Staff at the Oak Brook-based company’s suburban plant work preparing foods, such as Italian beef and sweet peppers, for local Portillo’s restaurants. Other members of the bargaining unit include forklift operators, mechanics and sanitation workers. The Addison facility, which is not a restaurant, is believed to be the first unionized Portillo’s location.

“We are thrilled the NLRB ruled against Portillo’s frivolous objections and hope it means Portillo’s will finally accept the workers decision, and negotiate,” said Brenda Bedolla, an organizer with the Iron Workers.

“I feel very happy because once again, we demonstrated to Portillo’s that our union election was clean,” said Portillo’s worker Fernando Jimenez, who has worked at the facility for more than three decades.

“We want them to finally sit down and negotiate our contract, and stop spending money on union busting,” Jimenez said.

Arise has previously accused Portillo’s of utilizing “an onslaught of company intimidation, false claims, mandatory captive audience meetings, and retaliation.” The union has filed unfair labor practice charges with the NLRB alleging illegal interrogation and coercion of workers at the Addison plant that remain under investigation, according to labor board records.

Portillo’s, which was founded in a Villa Park parking lot in 1963, has more than 70 locations across 10 states and is planning an aggressive expansion. At an investor day conference in September, the company said it aimed to hit a target of about 920 restaurants over the next 20 years. Most of those stores — about 800 — would be full-service restaurants, the company said, with the rest planned as walk-up restaurants in dense urban areas.

The company has eyed expansion in the Sun Belt in particular, opening a handful of stores over the last year in Florida, Texas and Arizona.

Portillo’s, which went public in 2021, posted revenues of $166.8 million during the third quarter, up more than 10% over the same period last year.