Secretary of State Rex Tillerson said the U.S. is evaluating whether to close the American embassy in Cuba after diplomats have come down with mysterious illnesses at the building.

"We have it under evaluation and it's a very serious issue with respect to the harm some individuals have suffered," Tillerson said Sunday on "Face The Nation."

"We have brought some of those individuals home and it's under review."

The statement may shake up relations between Cuba and the United States.

Former President Barack Obama normalized relations with the Caribbean island nation two years ago, but since then, multiple American diplomats have fallen ill and received serious injuries.

Speculation on what's causing the incidents in the embassy includes sonic attacks on diplomats.

The State Department said last month "some" U.S. diplomats in Havana reported "incidents which have caused a variety of physical symptoms," including hearing loss, nausea, headaches, and balance disorders.