The United States is looking into the matter of “unconfirmed” reports that Russia has opened a criminal case against a United States citizen on suspicion of espionage, State Department deputy spokesperson Vedant Patel told reporters on Thursday.

Patel said Russia does not generally abide by obligations to provide timely notification of the detention of U.S. citizens in Russia, adding that Washington would continue to monitor the situation.

The FSB did not name the person or provide any other details, nor did it say whether the suspect had been arrested.