US officials say fewer prisoners released from the detention center at Guantanamo Bay, Cuba, are returning to the fight than before.
But they acknowledged during congressional testimony Wednesday that Americans have been killed by released Guantanamo detainees.
The officials declined to provide details and did not say whether the incidents occurred before or after President Barack Obama took office in January 2009.
Their remarks triggered criticism from Republicans on the House Foreign Affairs Committee over Obama's intent to close the facility and house the remaining prisoners elsewhere.
The special envoys leading the facility's closure say it is a tragedy anytime a person is killed by a former detainee. Buy they say the risk of keeping the detention center open outweighs the risk of any transfer.
