(CNN) Cuba's foreign ministry said Sunday that it has not uncovered the cause of mysterious health symptoms that affected an official of the US embassy in Havana last month and characterized the United States' decision to withdraw personnel posted there as "politically motivated."

In a statement, the Cuban ministry said officials launched an investigation after learning an employee had "reported health symptoms as a result of 'undefined sound' in her place of residence." According to the statement, authorities could not find the source of the sound.

"After more than a year of research by the specialized agencies and experts from Cuba and the United States, it is confirmed that there is no credible hypothesis or conclusions adhered to science that justify the actions taken by the government of the United States against Cuba to the detriment of the bilateral relationship and with obvious political motivations," the statement said.

The Cuban response comes after the US withdrew two more people from the US embassy in Havana, Cuba, due to health concerns, according to a senior State Department official.

The individuals in the "potentially new cases" of a mystery illness that has plagued embassy employees have undergone medical evaluations and were not yet "medically confirmed," the official said.

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