A group of American oil executives held in a crowded Venezuelan prison were released to house arrest Friday, according to a person briefed on the negotiations.

The employees of Houston-based Citgo Petroleum Corp. were released from prison and granted house arrest in Caracas. Known as the Citgo Six, Tomeu Vadell, Alirio Zambrano, Jose Luis Zambrano, Gustavo Cardenas, Jorge Toledo and Jose Pereira were sentenced to lengthy prison terms in November on corruption charges.

U.S. officials tracking their case have suspected that Venezuelan President Nicolás Maduro might use it to appeal to the Biden administration as his country slips into deeper economic turmoil, exacerbated by the Covid-19 pandemic.

The release of the men to house arrest Friday was earlier reported by the Associated Press.

The six executives have been detained in Venezuela since November 2017, when they received a call from the Venezuelan oil company, Petróleos de Venezuela SA, summoning them to Caracas for a budget meeting.

When they arrived, armed and masked security agents arrested them. The executives were accused of embezzlement and money laundering tied to a proposed $4 billion financing deal that was never executed.

The families of the men—five of whom are naturalized U.S. citizens and one a U.S. resident—have complained that they have endured inhumane conditions, sharing crowded basement cells in a military counterintelligence prison and suffering from severe weight loss.