Washington: The disappearance of a former Guantanamo Bay prisoner who was transferred to Uruguay is sharpening debate in Washington over the wartime prison, even as a House committee prepares to hold an oversight hearing on Thursday about the Obama administration’s policy on releasing detainees to other countries.

The former detainee, Jihad Diyab, is a Syrian who was among six lower-level detainees resettled in Uruguay in December 2014. Early last month, he told several people that he was going on a religious retreat that would last beyond Ramadan and into next week – and that he would be unreachable by telephone or email.

Since then, some Uruguayan officials have said they lost track of him, and suggested that he may have crossed the largely unguarded border into Brazil. Heightening tensions, a Colombia-based airline asked its employees to alert authorities if they came into contact with him.

On Wednesday, Alexandre Moraes, Brazil’s justice minister, told reporters that “there is no sign” he was in Brazil. In Uruguay, Fernando Gil, a spokesman for the Interior Ministry, said Uruguayan authorities were not hunting for him. “As far as Uruguay is concerned, the person is here in the country,” Gil said.

He added that in an area such as the city of Chuy, which straddles the border with Brazil and has a Muslim community, “you can go from one side to the other and nobody controls it.”

Much remains unclear, and the disappearance has been greeted with different interpretations.

Representative Ed Royce, the Republican from California, and the chairman of the House Foreign Affairs Committee, said the disappearance showed that the Obama administration was “pushing dangerous detainees to countries that it knows can’t handle them,” and he called for a halt to all future transfers.

Some media stories have portrayed Diyab as a dangerous terrorist now in Brazil ahead of next month’s Olympic Games.

But Diyab’s friends and supporters portrayed him as someone who is physically impaired – needing crutches to walk. They believe he is simply praying and meditating somewhere and will resurface soon.

Jon Eisenberg, a lawyer representing Diyab in an effort to make public videos of his force-feeding during hunger-strike protests at Guantanamo, said he spoke to him on June 5. Diyab said that he would be incommunicado until a week after Ramadan, and that the priority his client put on those legal efforts was “quite inconsistent with the notion of simultaneously making himself a fugitive”, Eisenberg said.

Belela Herrera, a former deputy foreign minister for Uruguay who has been part of Diyab’s support network, said he also told her he would be gone until a week after Ramadan. She said it would be an odd time for him to become a fugitive because his wife and children from Syria are about to join him in Uruguay.

“I expect him to come back because his family is ready to join him,” she said in an interview. “He said he is going to relax and cut off all communications – and he hasn’t taken a mobile phone or anything at all – to prepare himself for the arrival of his family.”

Either way, it appears that the Uruguayan authorities did lose track of Diyab and that he may have crossed into Brazil, at least temporarily. Republican congressional staff members said that during Thursday’s hearings, Royce would focus on whether to send detainees to Uruguay, which has a porous border.

Royce has called as witnesses the top State and Defence department envoys for negotiating Guantanamo transfers, Lee Wolosky and Paul Lewis. At a hearing in March, Wolosky testified that the administration was confident that Uruguay was “taking appropriate steps to substantially mitigate the risk associated with each of the six detainees that have been transferred to its custody”.

Last week, Wolosky and Lewis travelled to Uruguay and spoke with senior officials there about Diyab’s case, several other officials said. Officials said that Diyab had no passport. Without one, he would be unable to obtain the visa he needs to lawfully travel to Brazil.

Still, Brazil and Uruguay are part of the so-called Mercosur region, which permits their citizens to freely cross borders. And Uruguay did issue Diyab an identification card in line with his status as a refugee. It looks the same as what most Uruguayans use, although it states his nationality is Syrian.

A Republican congressional official said an investigator sent by Royce to Uruguay reported that border guards rarely inspected such identification cards to see if the holder needed a visa – where the border has guards at all.

Myles Caggins, a National Security Council spokesman at the White House, said Wednesday that Diyab was on the “no-fly list,” which would prevent him from coming to the United States.

“We are aware of reports that he may have travelled from Uruguay to Brazil,” Caggins said. “We remain in close contact with our partners, Brazil and Uruguay on this matter.”