Amazon is being accused of religious discrimination and retaliation by three Muslim workers in Minnesota who say the tech giant denied them time and space to pray, and routinely assigned them less favorable work than their white counterparts, according to a federal complaint filed last week.

The workers, all black women from Somalia, say Amazon created a hostile environment for Muslim workers at its warehouse in Shakopee. They also allege that Somali and East African workers were denied promotions and training that went to white workers, and were relegated to more difficult tasks, like packing heavy items.

“Amazon is one of the largest employers in Minnesota and it relies on these workers to make billions, but it is withholding these basic accommodations as required by law,” said Nabihah Maqbool, an attorney for Muslim Advocates, a nonprofit organization that is representing the women. “Our clients are being monitored in their warehouses in such a way that they fear each day that they will be fired when they go to work.”

She added that many of the facility’s workers are from East Africa, while the “vast majority” of managers are white.

Seattle-based Amazon has repeatedly come under fire for its treatment of workers, particularly at its 110 warehouse facilities, where physical demands can be grueling.

Last year, it raised starting wages to $15 an hour following criticism from Sen. Bernie Sanders, I-Vt., and others that too many of its workers were relying on food stamps, Medicare and other government programs to make ends meet. Amazon has more than 250,000 hourly workers at its U.S. warehouses, making it one of the country’s largest employers. (Amazon’s founder and chief executive, Jeff Bezos, owns the Washington Post.)

The complaint in Minnesota comes on the heels of another recent report that at least seven women have filed lawsuits against Amazon accusing the company of pregnancy discrimination and retaliation. The workers allege that Amazon did not make accommodations for requests such as longer bathroom breaks and fewer continuous hours on their feet, according to CNET, which reviewed the lawsuits. All seven women were also fired after informing managers about their pregnancies, CNET said.

Amazon has disputed those claims: “It is absolutely not true that Amazon would fire any employee for being pregnant,” a spokeswoman told CNET. “We are an equal opportunity employer.”

In Minnesota, workers say they worried about taking breaks to pray or go to the bathroom because they were under pressure to meet certain quotas. Failing to make those “rates,” they said in their complaint, could result in a written warning that could eventually lead to their firing. The women also said the lack of air conditioning at the warehouse made it difficult to fast during Ramadan.

Two of the three women who filed the claim with the Equal Employment Opportunity Commission continue to work at Amazon; one was “constructively discharged” at the end of December.

“The heavy items make it so difficult to make the rate,” one of the women said in an email. She spoke on the condition of anonymity because she still works at the company and fears reprisal. “I don’t have even a second to speak with the associate next to me, or take a break, or drink water. When I go to pray I worry what will happen with the rate.”

Amazon spokeswoman Ashley Robinson said prayer breaks shorter than 20 minutes are paid, as required by law, and that employees can request longer unpaid prayer breaks “for which productivity expectations would be adjusted.”

The workers also accuse Amazon of illegally retaliating against them after they participated in a December event protesting discrimination at the warehouse. All three women said they “noticed a campaign of retaliatory harassment” that included more difficult assignments and increased surveillance. One worker said supervisors began recording her day-to-day conversations on video.

“Amazon’s message to Somali workers has been clear: Since they protested Amazon’s discriminatory actions, Amazon management would now create an environment so harassing and hostile that they would be forced to quit,” Muslim Advocates wrote in a letter to the Equal Employment Opportunity Commission.

“These women are not alone,” the letter continued. “The conditions described in their charges reflect a broader pattern and practice of unlawful employment discrimination against Muslim, Somali, and East African workers at Amazon.”