In a letter to congressional leaders released Monday, the counterterror chief for President Barack Obama says that a review has found that no detainees released on Obama's watch have returned to terror -- but that in cases where they may have, the Bush Administration was responsible. (Read the letter in PDF format by clicking the image below.)

"I want to underscore the fact that all of these cases relate to detainees released during the previous administration and under the prior detainee review process," assistant to President Obama for homeland security and counterterrorism John Brennan wrote in a letter to House Speaker Nancy Pelosi (D-CA), obtained by ABC News. "The report indicates no confirmed or suspected recidivists among detainees transferred during this Administration, although we recognize the ongoing risk that detainees could engage in such activity."

Jake Tapper of ABC News first posted the letter online.

The "Intelligence Community assesses that 20 percent of detainees transferred from Guantanamo are confirmed or suspected of recidivist activity," Brennan adds, saying that about 9.6 percent are allegedly "confirmed" to have returned to militant activity, with another 10 percent being suspected.

The review was conducted by "60 career prosecutors, agents, analysts and attorneys from across the government, including civilian, military, and intelligence officials," Brennan wrote. "Every decision to transfer a detainee to a foreign country during this Administration has been made unanimously by all agencies involved with the review process after a full assessment of intelligence and threat information."

According to Tapper, classified information was also included with the letter. That material has not been released publicly.

Pentagon claims for the recidivism of Gitmo detainees to terrorist activity have been hotly contested.

According to an analysis by a New Jersey law professor conducted in 2009, the Pentagon’s recent survey alleging that one in seven Guantanamo Bay prisoners return to terrorism was deeply flawed.

His analysis revealed the Pentagon had refused to identify 60 percent of the men they claim have returned to terrorism, saying the information was classified.

The 2009 recidivism analysis documents 74 recidivists, but lacks 45 names, adding that of the 29 names given, only half are labeled “confirmed” recidivists. Seton Hall University Professor Mark Denbeaux, who wrote the report, also alleges the analysis includes men who were never held at Guantanamo.

All told, 45 of 74 is 61 percent.