A CHEAP DIGITAL watch manufactured by Casio was identified as a potential sign that its wearer had received bomb-making training from al-Qaeda, according to secret United States documents on its military prison at Guantánamo Bay published today.

The documents, obtained by the New York Times and simultaneously published by the Guardian and by the US National Public Radio network, showed that the Casio F-91W digital watch had been identified by the United States as a possible sign that its wearer had been given training in manufacturing explosives by al-Qaeda in Afghanistan.

The documents also show how many innocent prisoners were help captive at the military prison in Cuba on wafer-thin suspicions – some of which were extracted only after brutal torture – and held alongside the “worst of the worst” offenders for years at a time.

The files also reveal that some of the inmates who were ultimately found to be entirely innocent included an 89-year-old man who suffered from senile dementia, as well as a 14-year-old boy who had simply been kidnapped and conscripted into fighting for the Taliban.

100 captives were diagnosed with depressive or psychotic illnesses, while others were held even though authorities had established that they were not members of the Taliban or al-Qaeda.

One Al-Jazeera journalist was also held for six years, partly so that he could be interrogated about the news network and its sources.

While the bulk of the 172 prisoners who remain in custody at the prison are classified as posing a “high risk” (meaning they would be considered highly dangerous if they were to be released), the documents also reveal that a third of the 600-or-so prisoners previously held there – many of whom have since been released entirely.

The Pentagon has condemned the release of the secret details, which the New York Times said have been given to it by an anonymous source not involved in the WikiLeaks whistle-blowing website.

Although the documents were among those held by WikiLeaks, the Times said WikiLeaks had not authorised their publication. They had only been released, the paper said, when a second source had supplied the documents independently and sanctioned their release.

WikiLeaks has itself published the files on its own websites within the last few hours – most likely in response to their publication elsewhere.