"It looked like it was an escape," Brigadier General Mark Kimmitt told a news conference in Baghdad on Sunday.
A US patrol found Hamill south of Tikrit, the home town of ousted leader Saddam Hussein.
"Preliminary reports that we have would indicate that he had escaped from a building. When he saw the American forces, identified himself and was subsequently recovered," Kimmit said.
Back to work
Hamill, who worked from a subsidiary of the US Halliburton company, is thought to be the only survivor from an assault on a convoy west of Baghdad on 9 April. Several contractors and two US soldiers were missing after the attack.
The Italian hostages work for a
US security firm
Hamill's captors threatened to kill or maim him unless US forces lifted their siege of the city of Falluja.
Asked how long Hamill had been free before he was found, Kimmitt said: " We don't know that information. We will find that out, I'm sure that he will be glad to tell his story...
"He has spoken to his family and now is ready to get back to work."
Rejecting an offer
Meanwhile, an Iraqi Kurdish faction on Sunday rejected a purported offer from the captors of three Italian hostages to trade them for members of an Islamist group being held by Kurds in northern Iraq.
"We will not bow to anyone in order to release the fundamentalists," said Mamusta Saif al-Din, deputy chief of security of the Patriotic Union of Kurdistan (PUK), which has had a running conflict with Islamist groups in its territory.
"These extremists have caused us many problems and we don't wish to dig in our own wounds," he told Reuters in the PUK's northern Iraq power base of Sulaimaniya.
"We will not bow to anyone in order to release the fundamentalists"
Mamusta Saif al-Din,
Deputy chief of security of the Patriotic Union of Kurdistan
Three Italians working for a US security firm were kidnapped last month outside Baghdad during a wave of abductions of foreigners.
A fourth Italian kidnapped with them was murdered after the captors demanded the withdrawal of Italy's 2700 troops in Iraq.
In a statement received by Aljazeera last week, a group calling itself the Green Brigades offered to swap the Italians for members of its group being held by Iraqi Kurds.
PUK fighters, backed by US missiles and special forces, attacked the stronghold of Ansar al-Islam group - which Kurdish and US officials accuse of links to al-Qaida - during the Iraq war.
Kurdish and US military officials have accused the group of involvement in bomb attacks on civilian and US military targets across Iraq and the PUK rounded up more than a dozen of its members last month.