US, Canadian envoys in Cuba suffer mysterious injuries

American and Canadian diplomats in Cuba have been diagnosed with mild traumatic brain injuries and damage to their central nervous systems, according to medical records obtained Wednesday by CBS News.

"What has happened there is of great concern to the U.S. government," State Department spokeswoman Heather Nauert said in a press briefing, declining to elaborate.

The diplomats complained about symptoms ranging from hearing loss and nausea to headaches and balance disorders beginning in December last year, according to CBS.

The State Department earlier this month expelled two Cuban diplomats from Washington after U.S. officials in Havana reported the symptoms.

A definitive source for the attacks has not been identified but the State Department reminded the Cuban government of their obligation to protect diplomats.

“This is unprecedented. Hasn’t been seen anywhere before," Nauert said. “This is a matter that we take very seriously.”

A source familiar with these incidents said officials are investigating whether the diplomats were targets of a type of sonic attack directed at their homes, according to CBS. The source said reports of more attacks affecting U.S. embassy workers on the island continue, the report said.

The family of a Canadian diplomat was also affected and received treatment, Global Affairs Canada, the department in the Canadian government that manages Canada's diplomatic and consular relations, said in a statement.

“We are aware of unusual symptoms affecting Canadian and U.S. diplomatic personnel and their families in Havana,” Brianne Maxwell, a digital communications advisor with Global Affairs Canada, told Canadian media.

“The government is actively working – including with U.S. and Cuban authorities – to ascertain the cause.”

Nauert noted the incidents have caused a variety of physical symptoms and affected staff and employees have been provided with the "best medical care."

The number of diplomats affected has not been specified.