Workers at 77 King Soopers stores across the Denver metro area started a strike Thursday after months of negotiations between the union and the company and the expiration of their contract last month.

Members of the UFCW Local 7 voted to approve the strike representing about 10,000 workers across the affected stores, the union said in a news release on Monday. The union has alleged that King Soopers is using “union-busting tactics” by bringing in temporary workers to make up for union members who are on strike.

In a Jan. 31 news release from King Soopers, the company said it would be hiring temporary workers during the work stoppage, which the union plans to hold for two weeks.

Chris Lacey, a service manager and a part of the negotiation committee, told USA TODAY the strike revolves around the company's unfair labor practices.

"We want them to come back to the table and we want them to realistically hear our staffing concerns," Lacey said. "We love our customers, we love the support we're receiving from our customers and we're in this fight to make better stores for our customers and better stores for our associates."

Need a break? Play the USA TODAY Daily Crossword Puzzle.

Here is what to know.

Union alleges unfair labor practices

The union says its strike efforts are focused on what members call unfair labor practices carried out by the company during contract negotiations.

The union says King Soopers interrogated union members about the union’s bargaining and surveilled members in discussions with union staff, as well as threatening members with disciplinary actions and sending them home from work for wearing union merchandise.

The union says the company also insisted on using $8 million in health benefits for retirees to pay for active workers' wage increases.

“These are serious charges against Kroger-owned King Soopers. They have, and continue to, break the law and are trying to force us to accept a new contract that takes us backward. That’s not going to happen,” Connor Hall, a King Soopers worker, said in a union news release.

In a press release, King Soopers President Joe Kelley called the allegations by the union baseless.

"We want to be clear − the union’s call for a strike is not about wages, healthcare, or pensions. It is based on allegations we believe lack merit and have yet to be validated by the NLRB or any court,” Kelley said.

King Soopers president calls demands 'unreasonable'

In a video to employees, Kelley said the union is using "unchecked power to create uncertainty,” as well as forcing customers to go to other stores in the area, "all because of reckless tactics."

Kelley said in a Monday release that the union should return to the bargaining table, calling their demands “unreasonable.”

“It is time to put aside their unreasonable demands, false rhetoric and headline-seeking tactics and work towards a fair and timely resolution that increases associates' pay while keeping groceries affordable,” Kelley said.

King Soopers says its workers earn an average hourly rate of $22.68.

In response to Kelley calling the union demands unreasonable, Lacey said the president's comments were insulting.

"I think it's insulting that he thinks our demands for better staffing for our customers, a better livable wage for our members is unreasonable," Lacey said. "He's been in the news a lot talking about how he has a responsibility to the customers and not one time has he ever mentioned that he has a responsibility to us as well."

Which stores are on strike?

According to a Thursday press release from King Soopers, locations that are included in the strike will have shortened open hours.

The company says the strike-affected stores will be open from 7 a.m. to 8 p.m. local time every day, with pharmacies in these locations open from 9 a.m. to 7 p.m. Monday to Friday and 10 a.m. to 5 p.m. on Saturdays.

Here are the locations where workers are striking as of Thursday, according to UFCW 7. All locations are in Colorado.

Fernando Cervantes Jr. is a trending news reporter for USA TODAY. Reach him at [email protected] and follow him on X @fern_cerv_.