A federal judge on Monday ordered Najibullah Zazi, the 24-year old Denver-area shuttle-bus driver at the center of a terrorism investigation, to be held at least until a detention hearing set for Thursday.

Najibullah Zazi's lawyer, Arthur Folsom.
Ed Andrieski/AP Photo

Najibullah Zazi's attorney, Arthur Folsom, walks to the federal courthouse in Denver on Monday, Sept. 21, 2009.

Meanwhile, his father Mohammed Zazi, 53, was ordered to be released on a $50,000 unsecured bond and placed on home confinement while wearing an electronic monitoring device.

The father and son of Aurora, Colo. were arrested Saturday evening by Federal Bureau of Investigation agents and charged with lying to federal agents who were investigating a terrorism conspiracy, a federal crime.

The men were among a number of Afghan nationals kept under surveillance by FBI agents who suspected them of being part of a terrorist cell with the capability to make and explode bombs,.

According to what law enforcement sources have told NPR's Dina Temple-Raston, among the FBI's concerns was that the men were viewed by law enforcement authorities as the group most capable of carrying out terrorist attacks since 9/11.

Meanwhile, in New York City, another federal judge ordered Ahmad Wais Afzali, 37, an imam who authorities said had been in contact with the Zazis to be continue to be held.