The strike at a JBS-owned beef plant in Greeley stretched into its fourth day on Thursday.

About 3,800 union workers went on strike Monday morning after several months of contract negotiations between the beef processing giant and the United Food and Commercial Workers Local 7 union reached an impasse over pay and safety equipment.

UFCW has accused JBS of walking away from the bargaining table and threatening employees for striking, while JBS has accused the union of being the one to walk away without allowing employees to vote on the proposed wage increases offered by JBS.

The union has alleged JBS has not given wage increases that outpace inflation and increasing healthcare costs while also charging employees for lost safety equipment. In a letter to JBS, UFCW President Kim Cordova wrote that since 99% of the unionized employees voted to authorize a strike, that means the employees already did not approve of the contracts offered by JBS.

During the third day of the strike Wednesday, striking employees chanted “Sí, se puede,” meaning “Yes we can” in Spanish, 9NEWS reported. The union also held a news conference in which a rancher criticized the beef industry for “abusive corporate power” relating to how companies pay ranchers for their animals, 9NEWS reported.

On Wednesday, the National Right to Work Legal Defense Foundation issued a legal notice to union workers informing them that if they wish to return to work, they must resign their union membership or be subject to fines. The warning comes as the federal labor board is investigating UFCW Local 7 for allegedly fining Denver-area King Soopers employees illegally after they resigned their union membership in order to work during an ordered strike.

Due to the strike, JBS said it has shifted production to other plants to prevent a disruption to the beef supply. JBS is the world’s largest meatpacking company and is the No. 1 beef producer in the United States.

Hailey Fishel, a JBS USA spokesperson, said in a statement to The Denver Gazette that “hundreds” of employees have reported to work amid the strike and that “we successfully operated the facility.” Fishel did not respond to a question asking for a more specific figure on the number of employees who chose to work.

“Our focus remains on running the facility as effectively as possible throughout the week,” Fishel said.

UFCW Local 7 did not respond to questions from The Denver Gazette regarding union fines and the allegation from JBS that the union walked away from bargaining without allowing for employees to vote on a new contract.

UFCW said in a statement that the strike will last for two weeks until JBS resolves its “unfair labor practices.”

The Denver Gazette’s news partners 9NEWS contributed to this story.