(Adds details on executives, background on case)
By Angus Berwick and Marianna Parraga
CARACAS/MEXICO CITY, Dec 9 (Reuters) - Venezuela has granted house arrest to six executives of U.S. refiner Citgo, a unit of Venezuelan state oil company PDVSA, who were jailed on corruption charges in Caracas in late 2017, three sources close to the case said on Monday.
U.S. Vice President Mike Pence and two U.S. senators had called on Venezuelan President Nicolas Maduro to release the six men, most of them U.S. citizens, citing concerns about their health.
Neither Venezuela's information ministry nor its chief prosecutor's office immediately responded to requests for comment. Citgo and the U.S. State Department also did not return requests to comment.
Former Citgo vice presidents Jose Luis Zambrano, Alirio Zambrano, Jorge Toledo, Tomeu Vadell and Gustavo Cardenas, and former President Jose Pereira had been arrested in November 2017 after being called into a meeting at the Caracas office of Petróleos de Venezuela, S.A., known as PDVSA.
The executives were accused of crimes including embezzlement, money laundering and conspiracy in connection with a never-concluded agreement to refinance Citgo debt. A Venezuelan court in June ruled that the six men should stand trial.
The conditions of their release on Monday from a detention center in Caracas run by Venezuela's military intelligence service prevent them from leaving the country, one source close to the men's defense team said.
Early this year, a group of 13 of the men's family members and lawyers wrote an open letter to the U.S. government asking the State Department and lawmakers to help win their release. Pence then met with their family members in April.
The men had "been forced to sleep with the lights on and experience severe heat, lack of air circulation, constant and untreated sickness, overcrowding, malnutrition, and seeing less than 30 minutes of sunlight per month," their families wrote in the letter.
Their arrests formed part of Maduro's self-declared corruption crackdown at PDVSA that led to dozens of executives being jailed, including former Citgo and PDVSA President Nelson Martinez. Martinez died in custody last December.
Venezuela opposition leader Juan Guaido took control of Houston-based Citgo, the government's crown jewel overseas asset, earlier this year after Washington recognized him as the country's legitimate president.
Guaido won the backing of the United States and some 50 other countries in January, but Maduro retains control of most state functions and the Venezuelan operations of PDVSA, which are under U.S-imposed sanctions. (Reporting by Angus Berwick and Luc Cohen in Caracas, and by Marianna Parraga in Mexico City; Editing by Richard Chang)