BOGOTA, Colombia (AP) — Venezuela’s former oil czar Rafael Ramirez was sued Friday by a Houston company that alleges he was behind demands for at least $10 million in bribes to sign off on deals to sell its energy assets in the South American country.

The civil complaint filed in Houston came just four days after a U.S. official told The Associated Press that Ramirez is suspected by prosecutors of having received bribes in connection to a major graft scheme at Venezuela’s state-run oil company, PDVSA.

In the new lawsuit, Harvest Natural Resources alleges that starting in 2012 it refused a $10 million bribe demand from a Florida-based oil consultant who said he was acting in the name of Ramirez, then PDVSA’s president and Venezuela’s oil minister. The company had reached an agreement to sell its stake in a joint venture with PDVSA for $725 million to Indonesia’s state-owned Pertamina.

Harvest claims that as a result of its refusal to pay up, Ramirez failed to approve the sale and the deal fell through. The complaint cited press reports in which Ramirez was quoted as saying that Venezuela was still analyzing the proposed sale and that “both the buyer and seller know what they need to do in order to obtain government approval.”

Ramirez, contacted Friday by AP, declined to comment on the suit but reiterated that he never asked for bribes or played a role in the selection of PDVSA’s business partners.

In 2013, Harvest says, it found another buyer, Argentina’s Pluspetrol, but was once again blocked by a similar pay-to-play scheme, the complaint charges. Ramirez’s successor as PDVSA chief, Eulogio del Pino, sent a letter to Harvest in which he allegedly called for payment of a “bonus” to the Oil Ministry, then headed by Asdrubal Chavez, a cousin of Venezuela’s late socialist leader Hugo Chavez.

Del Pino is also named as a defendant in the complaint along with two men who allegedly acted as intermediaries, the Florida-based consultant, Juan Mendoza, and a former deputy oil minister, Jose Angel Gonzalez.

Harvest says it finally managed to sell its Venezuela assets for a quarter of the original price in 2016, after Ramirez had been removed from PDVSA and was serving as Venezuela’s ambassador to the United Nations. Shortly after that, the U.S. company delisted and ceased doing business.

“Harvest played by the rules and was punished for it — to the tune of $470 million — as foreign officials and less honorable companies lined each other’s pockets,” Dane Ball, a lawyer for Harvest, told AP.

In 2016, Venezuela’s opposition-led National Assembly said $11 billion went missing at PDVSA in the 2004-2014 period when Ramirez was in charge of the company. In 2015, the U.S. Treasury Department accused a bank in Andorra of laundering some $2 billion stolen from PDVSA.

Separately, Ramirez was named but not charged in an indictment partially unsealed Monday in Houston against five former PDVSA officials. The indictment alleges two of the charged individuals told businessmen that proceeds from bribes made in exchange for quick payments and contracts would be shared with a senior Venezuelan official.

That official was identified in the unsealed portion of the indictment only as “Official B.” The unidentified Venezuelan politician is Ramirez, a U.S. official told AP.

Ramirez is also the target of a separate criminal investigation in Venezuela, accused of taking a cut of oil contracts brokered by associates including his cousin. Del Pino and several other PDVSA officials were arrested in November in the same probe.

Ramirez has called the Venezuelan case retaliation for his decision to break with President Nicolas Maduro, who he has accused of running Venezuela’s once-thriving oil industry into the ground and abandoning Chavez’s revolutionary ideals.