The long-awaited trial of the Citgo Six — oil executives, including five U.S. citizens, detained in Venezuela on corruption charges for more than two years — failed to open as scheduled Wednesday, leaving fearful family members calling on the U.S. government to do more to protect their imprisoned fathers and husbands.

The six men were executives of Houston-based Citgo Petroleum Corp., an oil refiner formerly controlled by the government of President Nicolás Maduro. Control of the company changed last year after the Trump administration authorized Juan Guaidó, the opposition leader recognized as Venezuela’s rightful head of state by the United States and more than 50 other nations, to name a new board.

The six men were arrested during a business trip to Caracas in November 2017 and have since been charged with money laundering, embezzlement, racketeering and participating in organized crime. They deny all charges against them; the Trump administration has called for their immediate release.

The case has emerged as a major point of contention between the Maduro government and the Trump administration. U.S. officials say Maduro is a usurper who has repressed, tortured and killed his opponents. They have called for his ouster.

In December, 25 months into their detention, a Venezuelan court scheduled their trial for Wednesday. But lawyers and family members said a necessary transport order to bring the men to court had not been issued by early afternoon.

Attorneys for the men have been demanding their release on several grounds, citing their innocence but also the fact that Venezuelan law does not permit defendants to be held for more than two years without trial. The fragile health of at least two of the men has been cited in requests for humanitarian release.

The Venezuelan government has not provided any official notice of the men’s current whereabouts. But U.S. officials and family members say they have received information that the men were moved from house arrest this month to the Helicoide, the notorious Caracas prison run by the SEBIN, Maduro’s feared intelligence police. The transfer occurred Feb. 5, the day President Trump received Guaidó at the White House.

“The conclusion from the legal point of view is that the Citgo Six have been forcibly disappeared,” said Jesus Loreto, attorney for executive Tomeu Vadell. “Not one lawyer, not one family member, has been able to have written or verbal contact with them since they were taken from house arrest. This is a crime against humanity.”

Tarek William Saab, Venezuela’s attorney general, did not respond to a request for comment. Saab signaled this month that the trial would start soon.

“Within 12 days there will be an open trial against these people, who committed crimes against the Bolivarian Republic of Venezuela,” Saab told reporters in Caracas on Feb. 7. “We are not talking about hippies, singers or folklorists who came here to give a concert in a square and were detained. We are talking about alleged criminals, corrupt embezzlers of the national heritage who are being prosecuted for that.”

All six men — acting president and chief executive José Ángel Pereira and vice presidents Vadell, Gustavo Cárdenas, Jorge Toledo, Alirio Zambrano, José Luis Zambrano — were born in Venezuela. Five are naturalized U.S. citizens; one is a U.S. permanent resident.

Family members accuse the Maduro government of wrongfully arresting and imprisoning the men. But they’ve also criticized the Trump administration, saying Washington has not made their release a priority in its Venezuela policy, which has been focused on forcing Maduro from office.

“If these were six Americans from Kansas, this might be a different story,” said Cristina Vadell, daughter of Tomeu Vadell. “I think there has been some reluctance from the administration to get into this head-on.”

She said her family has repeatedly requested a meeting with Trump, to no avail. Her frustrations are shared by Maria Elena Cárdenas, wife of Gustavo Cárdenas. She recently posted a video of her disabled teenage son pleading with Trump to bring his father home.

“I can’t personally know what they are doing because they have never told me,” Cárdenas said. “But if you ask me, they are not doing enough.”

A State Department representative said liberating the men is a “top priority.”

“The safety of Americans and the freeing of prisoners is absolutely a top priority for the State Department, which is why we have been actively engaged in the case of the Citgo Six,” said the official, who spoke on the condition of anonymity to discuss the sensitive matter. “In the last two weeks we have met with members of one of the families who were visiting Washington and been in touch with two governments asking for their assistance.”

The official said the U.S. government “continues to develop lines of effort through viable channels toward the safe recovery of these Americans. Unfortunately the Maduro regime continues their wrongful detention, but the department will continue our efforts to free them.”

Dennysse Vadell, Tomeu’s wife, says she has seen her husband three times since his arrest but has been unable to contact him since his transfer to the Helicoide. When she visited him in July 2018, she says, she was shocked by his appearance.

“He used to weigh 220 and he was down to 160 pounds,” she said from their home in Lake Charles, La. “He looked a prisoner of war.”

She paused.

“We just want him back home,” she said.

Mariana Zuñiga in Caracas contributed to this report.