Three Muslim employees at an Amazon warehouse in Minneapolis say they "have experienced discriminatory treatment, hostile work environment, retaliation, and constructive discharge" at work, according to a letter written by Muslim Advocates.

The advocacy group says the three women, identified only as Ms. A, Ms. B. and Ms. C., are all black women of Somali origin. They feel they are being discriminated agains on the basis of their race, religion, and national origin — and they say they are not alone.

"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," the letter to the U.S. Equal Employment Opportunity Commission Minnesota area office reads.

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The three employees allege Amazon does not offer an adequate space to pray and that employees fear taking time to pray because they would loose time working. One client feared that if her "rate," or how many items a worker packs per hour, declined she would be fired.

"Employees who regularly fell short of the rate — simply because they attempted to observe their religious obligations to pray — faced repercussions such as 'write-ups' that could lead to termination," the letter reads.

A group of Amazon workers in Minnesota who are Somali refugees demanded better working conditions during a protest outside one of the retailer's warehouses in Shakopee, Minn., on December 14, 2018. Kerem Yucel / AFP/Getty Images

The women also allege Amazon consistently fails to promote East African employees. "Qualified Somali workers are regularly passed over for promotions in favor of white workers and white workers regularly receive better duty assignments and better treatment than their Somali counterparts solely on the basis of their race and/or their national origin," the advocacy group says in the letter.

Minnesota is home to some 30,000 immigrants from Somalia who started settling in the area in large numbers in the 1990s, CBS Minnesota reports. Somali immigrants make up a sizable portion of the 3,000 workers at the Amazon fulfillment center in Shakopee, Minnesota.

The employees say that when hundreds of East African workers at Amazon's Shakopee facility rallied for better conditions last December, the company retaliated against them. As a result of their participation in the protest, "Ms. A, Ms. B, and Ms. C began experiencing a campaign of retaliatory harassment from Amazon management," the letter claims.

The women say the retaliation has taken many forms, such as being given less favorable duty assignments. Ms. B. says her everyday conversations were video recorded by her supervisors. All three women received write-ups, which are precursors to termination. "When our clients attempted to report the improper write-ups to management or to Human Resources, Amazon has uniformly failed to adequately investigate or address their claims," the letter states.

Demonstrators during a protest at the Amazon fulfillment center in Shakopee, Minnesota, on December 14, 2018. Kerem Yucel / AFP/Getty Images

Muslim Advocates says Amazon's treatment violates Title VII and the Minnesota Human Rights Act, which makes it is illegal for employers to discriminate against workers in decisions of hiring, firing, assignments, and promotions.

In a statement to CBS News, Amazon said they "respect the privacy of employees and don't discuss complaints publicly."

"Diversity and inclusion is central to our business and company culture, and associates can pray whenever they choose," Amazon's statement read. "Prayer breaks less than 20 minutes are paid, and associates are welcome to request an unpaid prayer break for over 20 minutes for which productivity expectations would be adjusted. We encourage anyone to compare Amazon's pay, benefits, and workplace to other retailers, and to come take a tour and see firsthand."

Muslim Advocates says it hopes the the federal Equal Employment Opportunity Commission will prioritize the investigation of the Amazon workers' allegations. "The EEOC should find reasonable cause to believe that in Minnesota, Amazon has cultivated a hostile work environment and an environment of discrimination against its Muslim Somali and East African workers on the basis of their race, religion, and national origin," the letter says.