(CNN) -- An Internet outage and a hurricane threat led to a 24-hour delay and then outright cancellation of a pretrial hearing for five high-profile terrorism suspects detained at the U.S. military base at Guantanamo Bay, Cuba.
A Pentagon official said all court events were canceled and everyone was being flown back home as Tropical Storm Isaac churned in the Atlantic, threatening to become a hurricane.
Maximum-security detainees are housed in hardened buildings that will have no problem surviving a hurricane, the official said. Minimum-security prisoners were being moved to harder buildings.
Sirens blared Wednesday as the U.S. military base went into readiness mode.
A military judge was set to convene a pretrial hearing Wednesday for the five men accused of staging the September 11, 2001, terrorist attacks.
It was postponed 24 hours after a deadly freight train derailment near Baltimore damaged fiber-optic cables and cut off Internet service to the Guantanamo base.
The hearing, which continues the long and complicated process of bringing the five men to trial, was to have started Thursday before the bad weather disrupted things.
The start of the actual trial is probably still a year away.
The suspects include Khalid Sheikh Mohammed, the self-proclaimed mastermind of the September 11 attacks. If convicted, they face the death penalty.
When the pretrial hearing does get under way, the military judge is expected to review dozens of motions from both sides.
Defense lawyers told reporters Wednesday they will challenge legal restrictions on information they are permitted to raise in court or share with their clients.
Prosecutors want to keep from public view classified information and also unclassified materials that they consider detrimental to national security. That includes the suspects' knowledge of CIA interrogation methods.
The American Civil Liberties Union is also scheduled make its first appearance before the judge.
The organization filed a motion in May to deny the government's request to prevent the public from hearing all statements by the defendants about their torture and detention while in U.S. custody.
"For centuries the First Amendment has guaranteed open trials, and the government's claim that it can keep from the public the defendants' testimony about their memories of torture is legally untenable and morally abhorrent," said Hina Shamsi, director of the ACLU's National Security Project and the attorney who was to have argued the motion Thursday.
"There is an ongoing public debate about the fairness and transparency of the Guantanamo military commissions, and if the government succeeds in censoring torture testimony, the commissions will certainly not be seen as legitimate," Shamsi said.
On trial with Mohammed are Abdul Aziz Ali, Walid Muhammad Salih Mubarak bin 'Attash, Ramzi Binalshibh and Mustafa Ahmed Adam al Hawsawi. They were arraigned in May.
That 13-hour arraignment -- slowed by court disruptions -- afforded a rare glimpse of the suspects, who had not been seen publicly since January 2009, when they were first charged by a military tribunal.
Some suspects ignored the judge; others appeared to be reading. One even took his shirt off in court while his attorney was describing injuries she alleged he suffered while in custody.
All five men are charged with 2,976 counts of terrorism, hijacking aircraft, conspiracy, murder in violation of the law of war, attacking civilians, attacking civilian objects, intentionally causing serious bodily injury and destruction of property in violation of the law of war.
The charges allege that the five are "responsible for the planning and execution of the attacks of Sept. 11, 2001, in New York, Washington, D.C., and Shanksville, Pa., resulting in the killing of 2,976 people," the Defense Department said.
Though Mohammed, known by his initials KSM, confessed to organizing the attacks, his confession could be called into question during a trial.
A 2005 Justice Department memo -- released by the Obama administration -- revealed he had been waterboarded 183 times in March 2003. The technique, which simulates drowning, has been called torture by President Barack Obama and others.
The military initially charged Mohammed in 2008, but Obama stopped the case as part of his effort to close the U.S. detention center at Guantanamo Bay.
Unable to close the center, Obama attempted to move the case to federal court in New York in 2009, only to run into a political firestorm.
The plan was dropped after complaints about cost and security, and Attorney General Eric Holder announced in April 2011 that the five would face a military trial at Guantanamo. The decision was met with some criticism, including from the ACLU.
The hearing that was canceled Wednesday was originally set for June but was postponed at the request of defense lawyers.
Brig. Gen. Mark Martins, the chief prosecutor, said Wednesday that the target date for the opening of the trial is next July.
CNN's Chris Lawrence, Larry Shaughnessy and Moni Basu contributed to this report.