Canadian and American diplomats in Havana may have been victims of a hidden attack.

According to Global Affairs, at least one Canadian diplomat has received treatment for headaches and hearing loss.

The incidents started last October and left a group of US diplomats with severe hearing loss.

In a report released today, it was concluded the diplomats had been attacked with an advanced sonic weapon that operated outside the range of audible sound and had been deployed either inside or outside their residences.

The U.S. is also investigating whether a third country was involved as “payback” for actions the U.S. had taken elsewhere and to “drive a wedge between the U.S. and Cuba.”

The U.S. has already expelled two Cuban diplomats from Washington.

An official at Global Affairs Canada said the country is not at the point where it is ready to take reprisals since the investigation is still ongoing.