As many as 18 people broke into the post office at the Thompson Center in the Loop early Monday.
The group broke through the front door of the post office in the first block of West Randolph Street around 12:35 a.m., Chicago police said.
It was not known if anything was taken. Police said they were investigating the incident as an attempted burglary.
No one was in custody, police said.
The spokesman for the U.S. Postal Inspection Service, which was investigating the break-in, did not immediately respond to questions.
The post office will be closed until further notice, according to signs taped to the post office’s windows later Monday morning by a postal inspector.
The post office at the Thompson Center was broken into on Monday morning.
David Struett/Sun-Times