The cause of death was congestive heart failure, according to her rep Joanne Drake, a spokeswoman with the Reagan Library.
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"Mrs. Reagan will be buried at the Ronald Reagan Presidential Library in Simi Valley, California, next to her husband, Ronald Wilson Reagan, who died on June 5, 2004," Drake wrote in a statement.
Former U.S. First Lady Nancy Reagan Dead at 94
Prior to the funeral service, there will be an opportunity for members of the public to pay their respects at the Library.
"It is a very sad day," former Ronald Reagan Chief of Staff Ken Duberstein told NBC News. "Every time she was in the room, he was better, and every time he was in the room she was better. She brought a sense of class and dignity and elegance that everybody admired."
Her step-son Michael Reagan posted on Facebook: "She is once again with the man she loved. God Bless."
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"We remain grateful for Nancy Reagan's life, thankful for her guidance, and prayerful that she and her beloved husband are together again," President Barack Obama and First Lady Michelle Obama said in a statement.