The North Community Bank, 800 N. State St., was robbed just before 2 p.m., said Chicago FBI spokeswoman Joan Hyde, in an email.
The man went up to a teller and demanded money, Hyde said. He did not show a gun.
The robber then fled on foot, heading south on State Street.
The robber was described as a white man in his 40s, standing 5-foot-9 to 5-foot-10, according to updated FBI information late this afternoon. He was wearing Bears cap and a black-and-white plaid flannel jacket and the lower part of his face was covered with a dark scarf at the time of the robbery, according to the FBI.
Anyone with information about the robbery is asked to call the FBI at 312-421-6700 or call police.