(Reuters) - U.S. prosecutors on Monday announced charges against five former Venezuelan officials accused of soliciting bribes in exchange for helping vendors win favorable treatment from state oil company PDVSA, the latest case to stem from a $1 billion graft probe.

The indictment by the U.S. Justice Department was filed in federal court in Houston, Texas, and was made public after Spain on Friday extradited one of the former officials, Cesar Rincon, who was a general manager at PDVSA’s [PDVSA.UL], procurement unit Bariven.

Others charged included Nervis Villalobos, a former Venezuelan vice minister of energy; Rafael Reiter, who worked as PDVSA’s head of security and loss prevention; and Luis Carlos de Leon, a former official at a state-run electric company.

Those three like Rincon were arrested in Spain in October at the request of U.S. authorities amid a foreign bribery investigation into the financially struggling PDVSA, or Petroleos de Venezuela SA.

De Leon, Villalobos and Reiter remain in Spanish custody. The indictment also charged Alejandro Isturiz Chiesa, who was an assistant to Bariven’s president and remains at large.

All five face conspiracy and money laundering charges. De Leon and Villalobos were also charged with conspiring to violate the U.S. Foreign Corrupt Practices Act.

Fred Schwartz, a lawyer for Rincon, said he expected his 50-year-old client would plead not guilty when he is arraigned on March 6. Lawyers for the other defendants could not be immediately identified.

The case flowed out of a U.S. investigation into what prosecutors have previously called a $1 billion bribery plot involving payments to PDVSA officials that became public with the arrest of two businessmen in 2015.

The indictment announced on Monday said that from 2011 to 2013, the five Venezuelans sought bribes and kickbacks from vendors in exchange for helping them secure PDVSA contracts and gain priority over other vendors for outstanding invoices during its liquidity crisis.

The indictment said the five Venezuelans then used various companies and bank accounts in Switzerland, Curaçao and elsewhere to launder the money they received.

Among the vendors that they promised to help in exchange for bribes were Roberto Rincon, who was president of Tradequip Services & Marine, and Abraham Jose Shiera Bastidas, the manager of Vertix Instrumentos, the indictment said.

Both pleaded guilty in 2016 to conspiring to pay bribes to secure energy contracts. Eight other people have also pleaded guilty in connection with the U.S. investigation.