SWAT teams stormed at least one home in Tinley Park, a suburb south of the city. Although neither man was found, evidence suggested that both had been at the home just hours earlier, according to the FBI.
Some schools went on lockdown after being inundated with calls from nervous parents. Mike Byrne, a superintendent in Tinley Park, said "our parents are so emotionally charged right now" because of the school shootings in Connecticut.
The facility is one of the only skyscraper lockups in the world, and experts say its triangular shape was meant to make it easier to guard, theoretically reducing blind spots for guards. The only other escape from the nearly 40-year-old facility occurred in the mid-1980s, Cantor said.
Both Banks, 37, and Conley, 38, were wearing orange jumpsuits, but police believe they may have quickly changed into white T-shirts, gray sweatpants and white gym shoes. The FBI believes both men were in Tinley Park, a heavily wooded area about 25 miles south of Chicago. Authorities were scouring a local forest preserve in the afternoon.
Banks, known as the Second-Hand Bandit because he wore used clothes during his heists, was convicted last week of robbing two banks and attempting to rob two others. Authorities say he stole almost $600,000, and most of that still is missing.
During trial, he had to be restrained because he threatened to walk out of the courtroom. He acted as his own attorney and verbally sparred with the prosecutor, at times arguing that U.S. law didn't apply to him because he was a sovereign citizen of a group that was above state and federal law.
After he was convicted by U.S. District Judge Rebecca Pallmeyer, he said he would "be seeking retribution as well as damages," the Chicago Sun-Times and Chicago Tribune reported.