BARCELONA, Spain (AP) — Spanish police arrested a former deputy Venezuelan energy minister Thursday on a U.S. warrant for alleged involvement in $1 billion bribery scheme involving Venezuela's state-run oil company PDVSA.

Nervis Villalobos was arrested in Madrid by a police unit specialized in money laundering crimes on an indictment from federal prosecutors in Houston, a spokesman for Spain's Civil Guard told The Associated Press. The spokesman, who wasn't authorized to be named and spoke on condition of anonymity, said that as part of the ongoing sting Luis Carlos de Leon, a former official at a state-run electric company in Caracas, was also taken into custody along with a third, unnamed person who was an executive at PDVSA's procurement unit, Bariven.

Villalobos would be the first senior ex-official detained as part of a wide-ranging U.S. probe into corruption at PDVSA that has already led 10 businessmen to plead guilty for their roles in kickbacks to Venezuelan officials. In 2015, the U.S. Treasury Department accused a bank in Andorra of laundering some $2 billion stolen from PDVSA.

Much of the evidence stems from a case in Houston against two Venezuelan businessmen residing in the U.S., Roberto Rincon and Abraham Shiera, who in 2015 were charged with violating the foreign corrupt practices act by conspiring to pay bribes in exchange for contracts to build power generators for PDVSA. U.S. prosecutors in their indictment accused the two men of paying everything from a PDVSA official's $165,000 mortgage in Texas to picking up a $15,000 reservation for several company officials at the Fontainebleau Hotel in Miami Beach in order to win business.

Both men are out on bail awaiting sentencing. Prosecutors in Houston declined to comment.

Villalobos was for years the deputy minister in charge of electricity projects and on several occasions stepped in as Oil and Energy Minister when his then boss, longtime oil czar Rafael Ramirez, was on missions abroad.

Ramirez, who has not been charged, currently serves as Venezuela's ambassador to the United Nations. He has dismissed the U.S. investigations against PDVSA, which he led for a decade until 2014, as an attempt by Washington to undermine President Nicolas Maduro's socialist government.

It was not immediately possible to locate Leon or Villalobos. PDVSA and Venezuela's information ministry did not comment when contacted by the AP.

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AP Writer Jorge Rueda contributed to this report from Caracas, Venezuela. Goodman reported from Bogota, Colombia