Havana (CNN) A higher number of US and Canadian diplomats and their families are believed to have been attacked by a mystery sonic weapon in Havana than was initially reported, CNN has learned from two senior US government officials.

More than 10 US diplomats and family members received treatment after the months of harassing attacks, which began in mid-November 2016 and stopped this spring, said the US officials, who did not want to be identified because of the sensitive nature of the attacks and ongoing investigation.

Two US diplomats who were treated in the United States suffered long-term injuries including hearing loss as a result of the attacks and were unable to return to Cuba, three US government sources told CNN. Additional diplomats opted to leave their assignments in Cuba early, as a result of the harassment, the two US government officials told CNN.

State Department spokeswoman Heather Nauert said despite the incidents and staffing changes, the US Embassy in Havana is "fully operational."

In June, five Canadian diplomats and family members reported experiencing symptoms consistent with the attacks, the US government officials told CNN, which would mean further attacks were carried out at the same time Cuban officials were investigating the incidents.

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