Amazon warehouse workers in a suburb of Minneapolis are striking Monday, the first day of a two-day Amazon online sales event, to protest their working conditions.

Workers at an Amazon Fulfillment center in Shakopee, Minnesota are walking out for a six-hour period on Monday that will overlap with the morning and evening warehouse shifts. They say Amazon has only accelerated the pace of their work despite prior complaints that demands on them were so high as to be unsafe. Amazon employs more than 600,000 people around the world.

In a statement, a company spokesperson said Amazon did not expect any disruptions in its operations due to the strike. The warehouse in question employs roughly 1,500 people full-time, according to the statement.

“The fact is Amazon offers already what this outside organization is asking for,” the statement read.

Some Amazon employees working from Seattle headquarters have come out in support of the strike and are joining the temporary workers in Minnesota, according to a statement from the group Amazon Employees For Climate Justice signed by dozens of employees.

Rep. Ilhan Omar (D-MN) joined a similar rally in December. A spokesperson for Omar told The Daily Beast the congresswoman could not attend Monday’s rally due to a scheduling conflict. An East African immigrant workers’ association, the Awood Center, coordinated the rallies in conjunction with the Council on American-Islamic Relations and a local chapter Service Employees International Union.

The same day as the strike, a coalition of activists that includes former Amazon workers will deliver a sheaf of petitions to Jeff Bezos’ $80-million-dollar New York City apartment in protest of conditions in the company’s warehouses and its working relationship with U.S. Immigration and Customs Enforcement. Current Amazon employees have made similar demands of the company that have gone unheeded.

Amazon created Prime Day, a global two-day discount of hundreds of products, five years ago to tout Amazon Prime, its membership program that offers free shipping on online orders and a laundry list of other perks. According to Amazon CEO Jeff Bezos, Prime had 100 million paying members in April 2018. Amazon spends lavishly to promote Prime Day, covering its delivery packages with advertisements for discounts and paying Taylor Swift to anchor a high-profile concert. Consumers have reciprocated in the past, buying more than 100 million items in 24 hours in 2018.

Unions of Amazon workers in European countries like Spain and Germany have staged strikes on Prime Days in the past, but the walkout in Minnesota represents the first major action of its kind in the U.S. during the sales event.

Amazon’s relationship with its warehouse workers has become contentious in recent years, with workers describing long, backbreaking hours and being fired for taking bathroom breaks. The company has come under fire from critics who say its treatment of low-level workers contributes to income inequality: Jeff Bezos is the world’s wealthiest person thanks to Amazon, but his low-level workers often rely on food stamps.

Amazon has attempted to ameliorate tensions with its workforce of late by committing to a $15-an-hour minimum wage in 2018 and promising this week to invest $700 million in technical training for employees over the next six years.

The Awood Center did not immediately respond to a request for comment on the strike.

—Sam Brodey contributed reporting.