A group of GOP lawmakers, seeking to block administration efforts to close the prison, this week proposed legislation to slow the release of inmates. They said about 30% of those released have turned to terrorism since the facility began housing militants in 2002.
In a statement, a senior State Department official said 19% of detainees released before President Obama took office in 2009 had been confirmed to have turned to terrorism, and 14.3% were suspected of doing so.
The number of confirmed cases among those released since 2009 has fallen to 6.8%, with the rate of those suspected at 1.1%, according to the official, who declined to be identified under administration ground rules.
The official cited a September 2014 report from the Office of the Director of National Intelligence saying that nearly half of the confirmed recidivists, and more than one-third of the suspected recidivists, are dead or in custody.
The administration released 28 prisoners from the prison in 2014, and is expected to release more in the coming weeks.
"We know for a fact that roughly 30% of those who have been released have reentered the fight," McCain said in announcing the legislation.