Venezuela has arrested the manager of the Petropiar heavy crude upgrader, owned by state oil company PDVSA and U.S. major Chevron Corp., for alleged “irregularities” in contracts awarded in the oil-rich Orinoco Belt.

Francisco Velasquez was detained on May 13 and he remains behind bars in the city of Barcelona in the eastern state of Anzoategui, the prosecutor’s office said in a statement.

“The investigation began in 2015, after a complaint by PDVSA employees, who pointed out certain irregularities in the awarding of contracts with over-pricing of goods or services,” the statement read.

Reuters was unable to obtain comment from Velasquez.

President Nicolas Maduro’s socialist government and Petroleos de Venezuela SA, familiarly known as PDVSA, have repeatedly vowed to take steps to combat corruption, which has affected Venezuela and its oil industry for decades.

Opposition leaders have said PDVSA has been particularly crippled by malfeasance under 18 years of socialist rule. They say sporadic arrests are more the result of infighting among rival government factions than a concerted effort to root out wrongdoing.

A probe last year by the opposition-run Congress said $11 billion had gone missing from PDVSA. The government dismissed that as part of a right-wing smear campaign.

PDVSA and Chevron, which has a 30% stake in Petropiar, did not immediately respond to a request for comment.

Local media in 2016 published photos from Velasquez’s Instagram account that appear to show him and his partner enjoying a lavish life, complete with holidays in Rome and Aruba, a house in the Dominican Republic and a pink sports car.

The opposition says corrupt officials have enriched themselves on the back of a decade-long oil boom, while the majority of Venezuelans now struggle to eat three square meals a day amid food shortages and spiraling inflation.