Also on Thursday, the US military reported four marines and a soldier were killed in operations south and west of Baghdad.
The freed kidnap victims brought to nearly 50 the number of captives who have been either released by their captors or extricated by police.
About 30 of the hostages, mainly women and children, were released shortly after they were taken captive.
It is routine in Iraq for women to take their children to work.
One kidnap victim, a Shia Muslim, said he was set free on Wednesday night after showing the kidnappers a forged ID card listing him as a Sunni.
He said two hostages had been killed trying to escape. The man refused to give his name fearing retribution.
"As we were leaving the factory we were stopped by gunmen. They got on our buses and told us to put our heads down. Then they took us to a poultry farm," the man said.
"One of the gunmen told us to stand in one line and then asked the Sunnis to get out of the line. That's what I did. They asked me to prove that I am a Sunni, so I showed the forged ID and three others did the same. They released us," the man said.
A national security ministry official, who spoke on condition of anonymity because he was not authorised to speak to reporters, told The Associated Press that several anti-government fighters holding the kidnap victims were captured during the Thursday morning raid on the farm in the Mishada area, 30km north of the capital.
Saddam is on a hunger strike in
protest at his attorney's killing
Police operations were continuing in the area, the official said, in an attempt to locate the rest of the victims.
The chief lawyer representing Saddam Hussein and his seven co-defendants, meanwhile, said the men went on a hunger strike to protest against the killing of a lawyer on the defence team on Wednesday.
It was the third such killing in the 8-month-old trial.
The military said the four Marines were killed on Tuesday in al-Anbar province, three of them in a roadside bombing and a fourth in a separate operation.
A soldier died on Wednesday south of the capital, the military said, giving no further details.
"Three marines were assigned to Regimental Combat Team 5 and died after their vehicle hit an improvised explosive device, while one marine was assigned to 1st Marine Expeditionary Force and died after being attacked while conducting security operations," the military said in a statement on Thursday of the Tuesday incidents.
Al-Anbar has been a stronghold for anti-US fighters and the scene of repeated attacks of US forces and US-trained Iraqi police and army.