Images of Camp X-Ray at Guantanamo caused outrage
Pentagon officials say about 30 detainees have been transferred to the Guantanamo Bay detention centre from Afghanistan.
Earlier, the Pentagon had confirmed that 13 prisoners had been "transferred for release" in Afghanistan on Wednesday.
Most were Afghans, but there were a small number of Pakistanis, Pentagon officials said.
The total number of detainees at the US base on the island of Cuba now stands at about 680.
The Pentagon says the latest transfers to the base are mainly Afghan and had been held in Afghanistan until now.
The US has used the base to house what it terms "unlawful combatants" it encounters in its so-called war on terror.
'No longer a threat'
It has not granted them prisoner-of-war status, and none has been charged or stood before a judge - a fact harshly criticised by human rights groups.
Had they questioned us here in Afghanistan, it would have saved us a lot of trouble
Former Guantanamo Bay detainee
The BBC's Nick Childs in Washington says this growing criticism could have spurred on the latest releases - though in public Washington insists it is not responding to such pressure.
It says it has merely deemed that the men no longer pose a threat to US security.
The 13 men sent back to Afghanistan this week, after more than a year in detention and interrogation at the base, are being held in a police station in Kabul.
Authorities said they would conduct short interviews and check they are not wanted for other crimes.
Speaking to news agency Associated Press, the men said they had been released without compensation or an apology.
One showed reporters a blue sports bag containing trousers, sports shoes, a jacket, underwear and a bottle of shampoo.
The detainees are still behind bars in Kabul
He said that was all he had been given.
"I'm just angry that the Americans waited until we were in Guantanamo to interrogate us," said Mohammed Tahir.
"Had they questioned us here in Afghanistan, it would have saved us a lot of trouble.
"They could have realised a lot sooner that I was innocent."
'Forced to fight'
Another man described how, two or three times a week, his hands and feet were bound and he was interrogated.
"All the time they asked us, 'Where are you from? Are you Taleban? Were you in Pakistan? Why were you captured with the Taleban?" said
The men who were released all said they were forced to fight for the Taleban.
Although they are bitter about their long detentions, apart from the frequent interrogations none of the men had any other specific complaints about their prison treatment.
They said they were allowed to pray, ate three times a day and showered twice a week, according to AP.