Nabisco workers in five states are on strike over changes to work schedules and overtime being sought by the maker of Oreos, Ritz Crackers, Chips Ahoy! and other popular snack foods.

The walkout began on Aug. 10 at a biscuit bakery in Portland, Ore., and has since swelled to about 1,000 workers in Aurora, Colo., Richmond, Chicago and, as of Monday, a distribution center in Norcross, Ga. They are represented by the Bakery, Confectionery, Tobacco Workers and Grain Millers International Union (BCTGM), which earlier this summer was involved in a 19-day strike at a Frito-Lay plant in Kansas.

Nabisco’s Chicago-based parent, Mondelez International, continues to produce snacks with nonunion staff even though three of its four U.S. bakeries have been affected by the strike. Unionized workers in all five states are governed by a single contract that expired in May.

Union leaders say Nabisco is trying to squeeze more hours out of its staff while paying less overtime, even as some workers are taking 16-hour shifts to help meet a pandemic-fueled surge in snack food sales. They also are raising concerns over two recent factory closures in Georgia and New Jersey, which the union says is part of a broader campaign to move low-wage work to Mexico. And they’re calling on the company to restore their pensions, which were supplanted by a 401(k) plan three years ago.

Workers “are telling Nabisco to put an end to the outsourcing of jobs to Mexico and get off the ridiculous demand for contract concessions at a time when the company is making record profits,” BCTGM President Anthony Shelton said in a statement.

Mondelez contends it has negotiated in good faith but its offers were turned down by the union, according to a company statement. Officials are moving some workers off the traditional 9-to-5 work schedule, which it says is no longer sufficient given the abnormally high demand for its cookies, crackers and other snacks. It wants to shift some personnel to a 12-hour workday.

“Our goal has been — and continues to be — to bargain in good faith with the BCTGM leadership across our U.S. bakeries and sales distribution facilities to reach new contracts that continue to provide our employees with good wages and competitive benefits, including quality, affordable health care, and company-sponsored Enhanced Thrift Investment 401(k) Plans, while also taking steps to modernize some contract aspects which were written several decades ago,” the company said in a statement.

Mondelez denies that any jobs went to Mexico as a result of its recent factory closures. It is considering adding several new U.S. projects, including possible expansions in Richmond and Portland as well as the possibility of “repatriating” a Ritz sandwich cracker line to Chicago, according to informational materials released by the company.

“We as a company are committed to the U.S., and to U.S. manufacturing,” said Laurie Guzzinati, a company spokeswoman.

The strikes come at a time when businesses across the country are experiencing a protracted labor shortage, strengthening the hand of employed workers. It also coincides with spiking commodity prices that have padded the coffers of snack-makers like Nabisco, which reported a 12 percent gain in revenue for the most recent quarter.

At the same time, high demand is causing companies like Mondelez to retool their production processes. But many factory workers say they’re being squeezed in the push for profits.

Unionized workers at a few large snack-makers have sought to limit work hours. Workers at the Topeka Frito-Lay plant recently ended a 19-day strike that was driven by concerns over forced overtime and 84-hour workweeks.

Donald Woods, president of the local Nabisco union in Chicago, says the strike is being led by longtime workers there ― including some whose parents or grandparents worked at the Nabisco bakery in suburban Chicago― who are fed up with years of cost-cutting being carried out by a profitable multinational corporation.

Those concerns bubbled after the company sought financial concessions from an overworked, undercompensated workforce, he said.

“Our position is we’re understaffed,” Woods said. The company “wants to save every dime they can, and it just takes everything out of the workers. You’ve got the CEO who’s making 16 or 17 million a year in salary but you won’t pay into the pension fund?”

Chairman and CEO Dirk Van de Put had a total compensation of $16.8 million last year, according to corporate disclosures analyzed by the Economic Research Institute.

Mondelez closed at $61.87, down 0.6 percent, on Wednesday, giving it a market valuation of $86.5 billion.