The State Department knew the extent of acoustic attacks against American diplomats in Cuba weeks before disclosing the facts to the public, according to CBS News on Wednesday.

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At least 21 State Department personnel have been injured by what has been described as a "sophisticated" sonic weapon which caused traumatic brain injuries and hearing loss.

The tally of those affected has steadily risen since Aug. 9, when the State Department first acknowledged the unexplained attacks.

State Department spokeswoman Heather Nauert first revealed the attacks at a press briefing, hours after media broke the news. But CBS reported Wednesday that the department knew the number of people injured was in the double digits "weeks" beforehand.

According to CBS, the "recent updates" Nauert claimed to be reading about the attacks actually were from a document created weeks, if not months, prior.

"They for sure tried to keep the numbers secret," a source told CBS. The State Department did not respond to CBS's request for comment.

Five Canadian diplomats and members of their families were also affected.

Cuba's government has denied any involvement in the attacks.

Cuba "strictly observes its obligations to protect foreign diplomats in its soil," said a statement from Cuba's foreign ministry reported by CBS. "Cuba has never perpetrated actions of this nature, and has never permitted nor will it ever permit any third-party."