Security has been tightened at the Guantanamo Bay detention camp in Cuba as the US military expands its investigation into alleged espionage by members of staff there.
The army says working practices have been altered
"We don't presume that the two we know about is all there
is to it," General Peter Pace, vice chairman of the Joint Chiefs of Staff, said.
Two US servicemen working at the facility - Senior Airman Ahmad al-Halabi, a translator of Syrian origin, and Captain Youssef Yee, a Muslim chaplain - have been arrested on allegations of spying.
Mr al-Halabi faces 32 charges, including helping the enemy, and is accused of contacting Syrian diplomats - a charge Syria's Information Minister, Ahmad al-Hassan, has angrily denied.
The cases have raised US defence department fears about security at the base, where hundreds of suspected members of the al-Qaeda network and the Afghan Taleban are being held without charge
"We will chase these rabbits as far as we need to to find
out where they lead," General Pace said.
"Its premature for anybody, certainly me, to presume
that he (Mr Halabi) is guilty or that the charges against him lead to a
particular country, or a particular group of individuals.
"If it turns out that this guy is guilty, and it turns out that he was talking to Syria in some light, then that's an issue that the government will deal with at the time," General Pace added, saying that any possible links to Syria were being investigated.
Syria's information minister said the allegations that Mr Halabi was passing information to Syria were baseless and illogical, and that it was incredible that a translator working at the sensitive facility would not have undergone intelligence screening.
The defence department will not say if the cases are linked
"How could Syria have spies in Guantanamo? Is the CIA incapable of finding a trustworthy translator?" news agency AFP quoted him as saying.
The most serious charges Mr Halabi faces - of espionage and aiding the enemy - carry the death penalty, but officials say no decision has been made yet on a trial.
A military attorney representing Mr Halabi has denied the charges, telling the Washington Post newspaper: "Airman al-Halabi is not a spy and he is not a terrorist."
The US Air Force has said Mr Halabi's arrest and a preliminary hearing was kept secret until now "to protect ongoing
American army Muslim chaplain Captain Yee was arrested last week, but the US defence department is not saying whether the two cases are linked.
Given the sensitivity surrounding the base, any link between the two is bound to be a primary focus for investigators, says the BBC's Pentagon correspondent Nick Childs.
Mr Yee, formerly known as James Lee, worked as a spiritual adviser to the hundreds of captured al-Qaeda and Taleban suspects at the base.