Another Canadian diplomat has reported a traumatic brain injury while stationed in Cuba, bringing to 13 the total number of cases among diplomats and dependents with "unusual health symptoms."

The affected person is receiving medical attention, according to a statement from Global Affairs Canada, while the government continues to investigate the potential causes of the so-called Havana Syndrome.

"In light of this new information, a decision has been made to allow staff currently posted to Cuba to return to Canada if they wish," the statement read.

It's been more than a year since the last report of such an injury at the Canadian embassy in Havana. Several U.S. and Canadian diplomats and family members have been treated over the past two years after reporting strange concussion-like symptoms.

Both countries believe their diplomats have been targeted using an unknown technology, and both the FBI and RCMP are investigating. The U.S. has also imposed sanctions on Cuba over the attacks, though officials in both Washington and Ottawa believe that the Cuban government is probably telling the truth when it denies involvement.

A delegation of senior Canadian government officials will travel to Cuba next week to review the current operations and assess how to further reduce risks, the statement read.

Long hiatus between attacks

Last winter, Canada made some changes at its Havana mission in response to attacks that had affected 12 diplomats and their family members, including children. Havana became an "unaccompanied" posting, meaning family members were no longer encouraged to join diplomats in Havana.

Canada also renewed its personnel at the embassy, and found accommodation for the newcomers in a single compound rather than having them dispersed around the city in private homes and apartments. The new accommodations are not close to any U.S. diplomatic facility, lessening the chance that the Canadians in Havana are being confused with U.S. diplomats.

Prior to the newest case, the last Canadian to report symptoms was diagnosed last fall, but believed the original attack had occurred earlier that summer. The newest case — involving a career diplomat, according to government sources — comes after almost 18 months with no reported incident.

Universities studying effects

The most recent case is expected to be examined by a Dalhousie University neurologist who is looking into the effects of the brain injuries and their possible causes. Global Affairs Canada also sent some of its affected diplomats to the University of Pennsylvania, which has taken the lead in examining U.S. diplomatic personnel and family members at the request of the State Department.

Some of the U..S diplomats affected reported hearing strange noises before their symptoms appeared, or experiencing uncomfortable physical sensations.

Canadian government sources say that of the 12 Canadians who were previously affected, only one reported feeling a sensation of waves or pulses coming through the air. In all other cases, the Canadians became aware of their injuries when they began to experience symptoms.

In the newest case, the diplomat also could not recall any particular incident that might have triggered the symptoms.

Who's behind it?

U.S. officials have said that the attacks are not consistent with any known technology or weapon, but they believe they are deliberate and targeted. Some scientists have pointed to microwave technology as a possible culprit, but neither the U.S. nor the Canadian government has yet settled on an explanation.

The assumption is that the attacks are the work of a state actor with a presence in Cuba, but the timing of the incidents — which began during a period of U.S.-Cuban rapprochement — does not suggest Cuban official involvement.

Potential suspects include other governments such as Russia or China, or rogue elements within the Cuban regime, possibly colluding with a foreign government.