TORONTO (AP) — Canada’s foreign ministry said Monday that it is ordering families of diplomatic staff in Cuba to return home amid questions about mysterious health symptoms detected in 10 people who were stationed on the island.

Canadian diplomats will no longer be accompanied by family members in Cuba because of what it called “ongoing uncertainty” over the cause of the ailments, the ministry said in a statement. Spouses, children or even parents of diplomats already with them in Havana will begin leaving immediately.

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The move comes after 10 Canadians continue to show unexplained brain symptoms and after “medical information raised concerns for a new type of a possible acquired brain injury.” Symptoms have included dizziness, headaches and lack of ability to concentrate.

The U.S. State Department cut staff at its embassy in October because of similar symptoms affecting 24 American diplomats and dependents.

Former U.S. State Secretary of State Rex Tillerson said the symptoms resulted from “targeted attacks” but not who may have been behind them.

Cuba has repeatedly denied either involvement in or knowledge of any attacks and has said its own investigation into the illnesses has turned up no evidence of deliberate action. The United States has not accused Cuba of such action but has said Havana holds responsibility nonetheless, arguing that such incidents could not have occurred on the small, communist-run island without the knowledge of Cuban officials.

The Canadian government said results of an environmental assessment of diplomatic staff quarters in Havana, including tests of air and water quality, did not indicate anything that could point to a cause.

Questions emerged “more recently” with information from Canadian medical specialists involved in the evaluation of affected diplomats and dependents as well as from U.S. specialists that “raised concerns for a new type of a possible acquired brain injury,” the ministry said.

“Additional research is needed to better understand this. The cause remains unknown but could be human-made.”

Cuba is a favorite tourist destination for Canadians, but the foreign ministry said there is no evidence of any related ailments among Canadian travelers

The foreign ministry said Canada has a “positive and constructive relationship” with Cuba and has received close cooperation from the Cuban authorities since the health concerns surfaced in Canadians last spring.

The mysterious case has sent U.S.-Cuba relations plummeting from what had been a high point when the two countries, estranged for a half century, restored full diplomatic ties under President Barack Obama in 2015.