Authorities in Romania say 180 people are being questioned on suspicion of election fraud in a referendum on ousting the president in 2012.

A leader from the ruling Social Democratic Party, Liviu Dragnea, is being investigated by prosecutors on suspicion of masterminding the fraud, which allegedly included the use of names of dead or fictitious people. Dragnea, who was not among those questioned Friday in Bucharest, says he is innocent.

The probe centers on a plot to inflate voter numbers at a referendum promoted by the party to impeach President Traian Basescu. The effort failed because turnout was below the necessary 50 percent.

The probe comes ahead of the Nov. 2 presidential election in which the Social Democratic Party leader, Prime Minister Victor Ponta, is the favorite.