Mexico officials are expected to return Emilio Lozoya, the former director general of Petróleos Mexicanos (Pemex), back home by Friday to face corruption charges after extraditing him from Spain, but there could be even bigger news in the days and weeks to come.

Lozoya, the poster boy of Mexico’s energy reform, is aiming to launch a political bombshell upon his return, according to media reports. Mexico’s landmark energy reform, enacted in 2013, was not the result of the democratic will of the nation, but instead was beset with bribery and corruption, according to some of Lozoya’s critics, who include President Andrés Manuel López Obrador.

During his press conference on Monday, the president, aka AMLO, said Lozoya was ready to “inform” on what occurred during the presidency of his predecessor Enrique Peña Nieto. On Wednesday, López Obrador divulged even more, claiming corruption had led to the reform.

The argument is that the vote on the transformative legislation was greased by large sums of money including from Brazilian construction giant Odebrecht, the firm at the center of many corruption cases throughout Latin America, but not so far in Mexico.

Peña, of the Partido Revolucionario Institucional (PRI) party that held uninterrupted power from 1929 to 2000, has rejected all accusations of corruption. Critics have said that since the 1938 nationalization of the oil industry by the PRI, no PRI deputy had supported the call to privatize the energy sector. In 2013, however, energy reform was backed by all PRI deputies.

The PRI, at least in its heyday, had claimed to represent the Mexican political spectrum, barring a handful of renegades. Prominent among those outsiders was López Obrador, who decades ago during the nation’s oil boom was a radical leader of peasants opposing state-owned Pemex.

Today López Obrador leads the Movimiento Regeneración Nacional (Morena), a politically diverse alliance united less by ideology than by the personality of its leader. López Obrador rose to power vowing to fight corruption, and the case against Lozoya is considered the most high profile in that push.

The suave sophistication of Lozoya once made him a darling of the international investor community, where he held court in the road shows during the months in which Peña was president-elect in 2012. As soon as Peña was inaugurated, Lozoya was named director general of Pemex even though he had no previous experience in the oil business.

However, Lozoya’s eloquence did not lead to good management of Pemex, Mexico City-based analyst Arturo Carranza told NGI’s Mexico GPI

“Indeed, Lozoya’s leadership of Pemex left much to be desired,” he said. “He was unable to arrest the decline in production and he also appeared to be unable to respond to changes in the world oil market. In all, he was one of the worst Pemex chiefs of recent years.”

Still, Carranza said previous Pemex CEOs have not usually been questioned publicly about alleged wrongdoing. The longstanding Pemex union boss was also ousted by López Obrador over corruption, a move met with bipartisan support.

Lozoya was booted early in 2016 as Pemex performance plummeted. Now, four years later, after being held in a Spanish jail, he is heading back to Mexico to face charges. His attorney Javier Coello in February issued a warning.

“My client wasn’t acting of his own account,” Coello told reporters.