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One of Fidel Castro's sisters says in a memoir released Monday that she collaborated with the CIA against her brother, starting shortly after the United States' failed Bay of Pigs invasion of Cuba in 1961.

Juanita Castro, 76, initially supported her brother's 1959 overthrow of the Batista dictatorship but quickly grew disillusioned. In a Spanish-language memoir published by Santillana USA and co-written by journalist Maria Antonieta Collins, she says the wife of the Brazilian Ambassador to Cuba persuaded her to meet a CIA officer during a trip to Mexico in 1961.

By then, her house had already become a sanctuary for anti-communists, and Fidel Castro had warned her about getting involved with the "gusanos," or worms, as those who opposed the revolution were called.

Castro says in the book, "My Brothers Fidel and Raul. The Secret Story," that she traveled to Mexico City under the pretense of visiting her younger sister Enma. There she also secretly met a CIA officer who identified himself as "Enrique" at the elegant Camino Real hotel.

During the meeting, she expressed her concerns that those who supported Batista's overthrow but were not communists were being pushed out of the new government. Castro writes she agreed to help the CIA gather information but refused to accept money for her efforts and said she wanted no part in any violence.

"I want to be very clear that agreeing to collaborate with you does not signify that I will participate in any violent activity against my brother, nor any official in the regime," she told the agent. "This is my most important condition. And moreover, I would say it is the only condition."

"Enrique," whom Castro says she later learned was a CIA officer in Cuba named Tony Sforza, then asked her to smuggle messages, documents and money back into the country hidden in canned goods.

He told Castro she would receive information through shortwave radio communications. Castro chose a waltz and a song from the opera Madame Butterfly as the signals her handlers would use to let her know if they had information for her.

Castro said she remained on the island while her mother was alive, believing she was protected from the full wrath of her brother. Her mother died in 1963 and she fled Cuba the following year, eventually settling into a quiet life in Miami, where she ran a pharmacy until 2007 and is generally well regarded by other Cuban exiles.