(CBS NEWS) HAVANA — Frightening attacks on U.S. personnel in Havana struck the heart of America’s spy network in Cuba, with intelligence operatives among those attacked, CBS News’ Steve Dorsey confirmed.

According to The Associated Press, which first reported the targeting of intelligence operatives, the operatives were the first and most severely affected victims.

It wasn’t until U.S. spies, posted to the embassy under diplomatic cover, reported hearing bizarre sounds and experiencing even stranger physical effects that the United States realized something was wrong, individuals familiar with the situation said.

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