The Pentagon’s special envoy for closing the Guantánamo Bay prison facility, Paul Lewis, insisted on Thursday to Congress that the process of emptying the prison is being done in a “safe and responsible” manner, despite multiple former detainees confirmed to have once again joined jihadist groups.

Lewis, who testified alongside Lee Wolosky, his counterpart at the Department of State, did so as Obama administration officials scramble to help the government of Uruguay locate Jihad Ahmad Diyab, a former Guantánamo detainee living in the South American country who went missing last month and had expressed support for al-Qaeda.

“These transfers out of Gitmo are in the national security interest of the United States and are conducted in a safe and responsible manner,” Lewis told the House Foreign Relations Committee.

“We have put in place procedures that are comprehensive; they’re rigorous; they’re interagency in nature, and we believe that as a result of those procedures, that has contributed to the very substantial reduction in the re-engagement rates seen between both administrations,” Wolosky added.

House Foreign Relations Committee officials were highly skeptical of these claims. Rep. Ed Royce (R-CA), who chairs the committee, accused President Barack Obama of making “a political decision to close Guantánamo no matter what the cost to national security.” He accused Wolosky and Lewis specifically of issuing assurances regarding the safety of releasing detainees that resulted in risky national security situations, like the disappearance of former detainee Jihad Ahmad Diyab.

Diyab, who was released to Uruguay, went missing in mid-June, allegedly after traveling to the Brazilian border to observe Ramadan. The government of Uruguay claims he traveled to Brazil, but Brazilian officials have no record of him entering the country. Rumors surfacing on Thursday place Diyab in Venezuela. Diyab has claimed to not have been an al-Qaeda sympathizer at the time of his detention but that he learned to love the terrorist group at Guantánamo.

“It appears the assurances you got from Uruguay didn’t account for anything,” Royce told Wolosky at the committee hearing. “This fellow, Jihad Dhiab, walked right out of Uruguay. We have no idea where he is.”

“While we would have preferred that Mr. Dhiab remained in Uruguay, if in fact he is not in Uruguay currently, until the expiration of the two-year resettlement program that was the subject of the agreement reached with Uruguay and reached with him, frankly, the fact is that the standard is not elimination of risk, is it mitigation,” Wolosky replied.

Lewis had testified before the committee in March. At the time, he confirmed that released Guantánamo detainees had killed Americans after leaving the facility. “What I can tell you is unfortunately there have been Americans that have died because of [Guantánamo] detainees,” he admitted. “When anybody dies, it is tragedy and we don’t want anybody to die because we transfer detainees.”

Diyab is the latest in a series of former Guantánamo detainees to cause alarm among American officials, and he is only suspected of possibly involving himself once again in the global jihadist movement. At least one former detainee was arrested this week: Airat Vakhitov, a Russian national arrested in Turkey in connection with the siege on Istanbul’s Atatürk airport that left dozens killed and injured. Vakhitov had renounced his Russian citizenship after being released and was believed to have ties to the Taliban.

Another former Guantánamo detainee was arrested in Spain in February, his name never released. The man was believed to have been working with Sunni jihadist groups to plot attacks in Europe. That same month, Secretary of Defense Ashton Carter asserted that those detained at the facility on the island of Cuba were too dangerous to be let go to foreign countries. “[T]here are people there who cannot be safely transferred to the custody of another country,” he told Congress. If the facility is to close, he asserted, those populating it cannot be released abroad: “[T]hey’ve got to go somewhere, and if they’re not going to be at Guantánamo Bay, they have to be somewhere in the United States.”

A month before Carter’s testimony, the Pentagon announced the release of Muhammad Abd Al Rahman Awn Al-Shamrani, to Saudi Arabia. Al-Shamrani had explicitly stated before his release that he would seek to “kill Americans” if he was ever let out of the facility.

Another former detainee, Ibrahim Al Qosi, appeared in an al-Qaeda recruiting video in December urging more attacks on Americans.