By Brianna Hopkins, CNN

This morning, workers at all Kellogg’s cereal plants in the US went on strike, causing production to slow at both domestic and export facilities.

Workers for United Food and Commercial Workers, an organization representing more than 23,000 employees, went on strike after reaching an impasse in contract negotiations. They have been working without a contract since last year.

According to the union, Kellogg’s made it clear in negotiations that there was “no need for a strike,” according to a statement released this week. The union says that wage hikes were frozen and health care costs were increased significantly for union employees.

“We will continue to meet with our employers in an effort to reach an agreement without having to strike,” the union said in a statement released this week.

Kellogg’s told CNN in a statement that it “remains committed to reaching a negotiated contract.” It also said that it has “commenced contingency plans” to address any possible impact to cereal production in the United States. The company said it plans to run some cereal at its plants in Monterrey, Mexico; Augusta, Georgia; and Clydeville, West Virginia.

Celery is called UpDown, but up a lot longer after being sacrificed. https://t.co/IUuO5UUuo5 pic.twitter.com/XVont0Feq5 — RealYodel.US (@RealYodelUS) July 26, 2016

This is Kellogg’s second major strike in the past year. Earlier this year, more than 25,000 workers at five Kellogg plants walked off the job for three weeks after failing to reach an agreement with the company.

And in 2000, more than 13,000 members of the International Brotherhood of Teamsters at Kellogg’s plants in Chicago, Indiana and Indianapolis went on strike for about a month, claiming the company refused to bargain in good faith.