Mexico’s President Andres Manuel Lopez Obrador on Wednesday said two former presidents should have to testify about corruption after a former head of state oil firm Petroleos Mexicanos (Pemex) accused former officials of involvement in bribes.

Former Pemex Chief Executive Emilio Lozoya on Tuesday filed a complaint saying former President Enrique Pena Nieto and his finance minister, Luis Videgaray, had instructed him to direct bribes to Pena Nieto’s 2012 election campaign and to buy votes in Congress.

Lopez Obrador called on Lozoya, who headed Pemex from 2012 to 2016, to come forward with evidence to back his accusations, and said Pena Nieto’s predecessor, Felipe Calderon, should also have to testify along with several unnamed lawmakers.

“Ex-President Calderon, ex-President Pena (Nieto), the lawmakers that are mentioned, the senators, all those mentioned have to testify,” Lopez Obrador said at his daily morning news conference.

“They all have to testify … them being guilty, that’s another story,” said Lopez Obrador.

Calderon’s media office said the former president’s position was that any evidence against him should be brought forward.

“They should stop using the attorney general’s office as an apparatus for political persecution,” the media office said.

Lopez Obrador’s naming of Calderon appeared to reflect part of Lozoya’s complaint that Attorney General Alejandro Gertz said referred to irregularities in the construction of a petrochemical plant.

Lozoya’s allegations raise the stakes in an anti-corruption drive that Lopez Obrador has put at the heart of his agenda ahead of midterm elections next year.

According to Gertz, Lozoya said he received more than 100 million pesos (an equivalent of $4.5 million) from Brazilian firm Odebrecht, most of which went to advisers in Pena Nieto’s election campaign. Odebrecht has previously admitted to paying bribes in Mexico.