Phoenix Mayor Greg Stanton asked the Department of Justice and Attorney General Loretta Lynch to investigate voting delays in Maricopa County, Ariz., during Tuesday's primaries.

"Throughout the county, but especially in Phoenix, thousands of citizens waited in line for three, four, and even five hours to vote," Stanton wrote in his letter to Lynch on Thursday. "Many more simply could not afford to wait that long, and went home. This is unacceptable anywhere in the United States, and I am angry that County elections officials allowed it to happen in my city."

In the letter, Stanton notes that the total number of polling places in the county was cut significantly: by 85 percent compared with the 2008 primary, and 70 percent compared with the 2012 primary. This cutback was especially salient in minority communities.

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"In Phoenix, a majority-minority city, County officials allocated one polling location for every 108,000 residents. The rations were far more favorable in predominantly Anglo communities: In Cave Creek/Carefree, there was one polling location for 8,500 residents; in Paradise Valley, one for every 13,000 residents; in Fountain Hills, one for 22,500 residents; and in Peoria, one for every 54,000 residents," he wrote. "Because of the unacceptably disparate distribution of polling locations, I respectfully request the U.S. Department of Justice investigate what took place in Maricopa County to ensure all voters are treated equally under the law."

The Justice Department confirmed to CBS News that it has received a request and will review it.

Vermont Sen. Bernie Sanders praised Stanton's decision to call for an investigation. The Democratic candidate had previously spoken out about the issue, including sending a fundraising email on the topic following Tuesday's primary.

"I'm glad to see @MayorStanton asking @TheJusticeDept to investigate the voting delays in Arizona," he tweeted Thursday.

Clinton's campaign counsel, Marc Elias, also called in a post on Reddit for further investigation, saying he "shares the concerns" of those who have spoken out.