Prosecutors have informed former Romanian President Traian Basescu that he is under criminal investigation for making threatening remarks to a senator.

Basescu appeared before prosecutors for about 25 minutes Wednesday, where he was informed about the blackmail probe initiated by Sen. Gabriela Vranceanu Firea, a political rival.

Prosecutors said Basescu asked for time for his lawyers to study the file. Some 20 protesters gathered outside the prosecutor's office yelling: "Basescu, to prison with you!" He was president from 2004 to 2014.

Last year, while Basescu was still president, Vranceanu Firea accused Basescu's elder daughter of fraud related to a property restitution case. Basescu then publicly warned Firea Vranceanu to "be careful," saying one day she might not find her husband at home.