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U.S. Sen. Hillary Clinton (D-NY) placed her hand over her heart during the National Anthem at the 30th Harkin Steak Fry in Indianola, Iowa, in this Sept. 16, 2007 photo. Reuters/Joshua Lott

Several benefactors to the Clinton Foundation -- the nonprofit established in 2001 by former U.S. president Bill Clinton -- received favors from the U.S. State Department during Hillary Clinton’s tenure as secretary of state, according to a soon-to-be-released book accessed by the New York Times. The book, “Clinton Cash: The Untold Story of How and Why Foreign Governments and Businesses Helped Make Bill and Hillary Rich,” is scheduled to be released on May 5.

“We will see a pattern of financial transactions involving the Clintons that occurred contemporaneous with favorable U.S. policy decisions benefiting those providing the funds,” Peter Schweizer, a former research fellow at Stanford University's Hoover Institution, reportedly writes in the book. He also alleges that the Clintons have “conducted or facilitated” hundreds of transactions with foreign governments and individuals that have “put millions in their own pockets.”

According to the Times, the book describes, among other things, how the Clintons received over $1 million in payments from a major shareholder in the Keystone XL oil pipeline at a time when the project was being debated in the state department, and how Clinton family members were given major development projects in the aftermath of the Haitian earthquake in 2010.

“Clinton Cash reveals how the Clintons went from ‘dead broke’ on leaving the White House to being millionaires, describing in detail the way in which the Clintons habitually blur the lines between politics, philanthropy, and business,” HarperCollins, which is publishing the book, announced in a press release, adding that the book would detail several “questionable deals” made by Bill and Hillary Clinton.

This is not the first time the Clinton Foundation has come under criticism for accepting money from foreign individuals, corporations and governments. In a report published Saturday, Newsweek revealed that one of the foundation's biggest benefactors was a Ukrainian businessman named Victor Pinchuk.

Pinchuk, who is the fourth richest man in Ukraine, owns the Interpipe Group, which made a series of shipments of products related to oil and gas to Iran in 2011 and 2012, Newsweek reported. This is believed to be in violation of the current U.S. economic sanctions on Iran, which prohibit shipments worth more than $1 million to the Middle Eastern nation.

The workings of the Clinton Foundation have come under the spotlight since Hillary Clinton announced earlier this month that she'd seek the Democratic Party's nomination to run for president in the 2016 elections.