The steady stream of detainees being transferred out of Guantanamo Bay is raising security concerns among lawmakers who worry the Obama administration has no system for keeping tabs on them.

The latest batch includes four prisoners once classified as high risk, individuals ranging from a known weapons smuggler to a Taliban operative involved in multiple attacks against U.S. and coalition forces.

"They're very dangerous terrorists," Sen. Kelly Ayotte, R-N.H., told Fox News, after the four Afghan detainees were transferred to their home country over the weekend.

Administration officials have touted the transfers as part of fulfilling President Obama's commitment toward winding down the controversial prison camp. The administration has transferred 23 detainees out of the camp so far this year, with more transfers potentially coming before Dec. 31.

Secretary of State John Kerry this week touted "huge progress" in shrinking the detainee population, as he announced the departure of Cliff Sloan, the president's point man on the camp. Over Sloan's 18 months on the job, Kerry said in a statement, 34 detainees were moved out of the camp, "with more on the way."

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    It's unclear whether Sloan's departure might delay more transfers. Obama remains intent on closing down Guantanamo during his final two years in office, despite congressional and logistical hurdles -- like what to do with those too dangerous to release. But as the pace of transfers picks up, lawmakers worry the government is taking a big risk already.

    The most recent transfer involved four men classified as high risk. According to The Associated Press, outgoing Defense Secretary Chuck Hagel did not sign off on the transfer right away, after the top U.S. commander in the country, Gen. John Campbell, voiced concerns about the risk they would pose to troops. However, officials reportedly say the military has since screened the move; the Defense Department said in a statement the U.S. worked with the Afghan government to make sure the transfers are consistent "with appropriate security and humane treatment measures."

    This followed the release of six men to Uruguay and the release earlier this year of the "Taliban Five" to Qatar in exchange for Army Sgt. Bowe Bergdahl.

    The four that went to Afghanistan, with no requirement that they be detained, are:

    Mohammed Zahir 

    According to documents, Zahir was a high-level Taliban intelligence official arrested on suspicion of having, among other contraband, uranium. A 2008 Pentagon document, posted on WikiLeaks, said evidence indicated the uranium was intended for a nuclear device. He also was determined to be a weapons smuggler; he had been at Guantanamo since 2003.

    Abdul Ghani 

    Ghani was accused of being part of a dangerous Taliban militia unit that plotted kidnappings and attacks against U.S. and Afghan forces. According to a 2008 military document, he admitted taking part in one rocket attack against U.S. forces. He was accused of helping plant landmines and other explosives for attacks against U.S. and coalition forces, and providing rockets to others for attacks on U.S. forces.

    Khi Ali Gul 

    Gul originally fought against the Russians in the 1980s and later went on to be an intelligence chief for the Taliban regime. He allegedly helped plan a 2002 rocket attack against a coalition base in Afghanistan and was accused of involvement in other plots.

    Shawali Khan 

    Khan was accused of being involved with a group aligned with Al Qaeda and the Taliban. Informants claimed the cell he was involved with was behind planned attacks on U.S. forces in Afghanistan.

    The dossiers for the detainees released to Uruguay are along similar lines. One, Ali Husein Shaaban, allegedly participated in "hostilities" against U.S./coalition forces in Usama bin Laden's Tora Bora complex. Documents also say he got suicide operations training from a bin Laden associate.

    Other detainees released to the South American country have similar rap sheets.

    The backgrounds of the five Taliban commanders released in exchange for Bergdahl were detailed earlier this year. Among them is Abdul Haq Wasiq, who served as the Taliban's deputy minister of intelligence. He reportedly used his office to support Al Qaeda "and to assist Taliban personnel elude capture."

    Another, Mullah Mohammad Fazi, was a former deputy defense minister for the Taliban. He is also wanted by the United Nations on war crimes for the murder of thousands of Shiite Muslims in Afghanistan.

    John Bolton, former U.S. ambassador to the United Nations under the George W. Bush administration, warned that at this stage -- after hundreds of detainees have been transferred out -- the "hardcore of the hard core" are left.

    He told Fox News it's "inevitable" that many will return to the battlefield.

    A total of 132 detainees are left at the camp, down from the more than 700 prisoners it once held.

    "We're putting ourselves in danger, we're putting our allies in danger," Ayotte told Fox News. "[Obama] doesn't have a plan when it comes to making sure that those who are released don't get back in the battle."

    But Obama, in a signing statement attached to a newly approved defense bill, reiterated his call to close the camp and said the real threat is the facility's continued operation.

    "The Guantanamo detention facility's continued operation undermines our national security. We must close it. I call on Members from both sides of the aisle to work with us to bring this chapter of American history to a close," he wrote.