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By Alexandra Ulmer

CARACAS, Oct 26 (Reuters) - A top executive at Venezuelan state energy company PDVSA was arrested on Tuesday as part of a growing graft probe there, three people familiar with the situation told Reuters on Thursday.

Orlando Chacin leads PDVSA's CVP subsidiary, which looks after joint ventures with foreign partners, and was the right-hand man of the company's former president, Eulogio Del Pino, who is now the nation's oil minister.

Eight PDVSA executives in Venezuela's oil-producing Zulia region and Pedro Leon, a powerful executive who led the company's Orinoco Belt development, were detained in September.

Tarek Saab, Venezuela's new chief prosecutor, told Reuters last month that he expected further arrests in widening oil-sector bribery scandals. He was due to hold a media conference later on Thursday.

The prosecutor's office had said in July that it would charge Chacin under the country's anti-corruption law in a case involving overcharging and improper use of vehicles. PDVSA did not immediately respond to a request for comment.

President Nicolas Maduro's socialist government and PDVSA, which is formally known as Petroleos de Venezuela SA, have repeatedly vowed to take steps to combat corruption, which has affected the nation 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.

(Reporting by Alexandra Ulmer; Editing by Lisa Von Ahn)