The former head of Pemex, Mexico’s state oil company, has dropped his extradition fight and will be flown home from Spain to face charges in the biggest corruption prosecution yet under President López Obrador.

Attorney General Alejandro Gertz Manero said Emilio Lozoya had “offered his collaboration to establish and clarify the matters of which he has been accused.”

The former Pemex chief, who had been a key figure in the election campaign of former president Enrique Peña Nieto, was arrested at a luxury residential complex on the Costa del Sol in February, after an eight-month search.

Lozoya has denied receiving US $10 million in bribes from the Brazilian construction company Odebrecht, which admitted paying billions of dollars in kickbacks across Latin America in exchange for political favours that have landed scores of former officials across the region in jail.

He faces charges of money laundering and corruption over Pemex’s purchase of a fertilizer factory.

Shortly after news of his imminent extradition was made public, Coello Trello y Asociados, the law firm that represents Lozoya, said it would no longer do so.

In a statement, it said it had taken the decision a month ago, in agreement with Lozoya, but gave no reason.

Mexico was conducting final paperwork before sending an aircraft to fly him home. Once back in Mexico, legal proceedings would begin “immediately,” the attorney general said.

“The relevance of this issue mandates an absolutely transparent investigation and fairness that is beyond doubt,” he said.

That scandal, as well as the unsolved killing of 43 students almost six years ago, has tainted Peña Nieto’s reputation. Some analysts believed that Lozoya could testify against his former boss.

“He surely didn’t act alone,” said Marco Fernández, anti-corruption investigator at México Evalúa, a think tank, and a professor at the Tec de Monterrey. No other former officials have yet been accused.

“The big elephant in the room is the lack of results” in López Obrador’s anti-graft drive, he added.

Gertz Manero also said an Interpol red notice had been issued against Tomás Zerón, the fugitive former head of the Criminal Investigation Agency that was part of the attorney general’s office, seeking his extradition to face charges in connection with the investigation of the student killings.

Zerón had been a defender of what the previous government described as the “historic truth” — that the students had been kidnapped by corrupt police, handed to a local cartel, killed and burned.

“The historic truth is over,” Gertz Manero said.

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