A private plane with 10 US passengers and two crew members died after their plane crashed in Costa Rica.

Costa Rica's president, Luis Guillermo Solís, said an investigation would begin Monday into what caused the aircraft to go down shortly after 12 pm (1 pm ET) in Guanacaste, a province in the country's northwestern corner popular with international tourists.

Guillermo Solís didn't identify the victims. He said the plane belonged to a Costa Rican airline, Nature Air.

n a statement, the U.S. State Department confirmed the deaths of "multiple" Americans but declined to provide additional details.

"We express our condolences to all those affected by this tragedy," the statement said. "We are in contact with Costa Rican aviation authorities and will continue to monitor the situation."