Authorities say that they believe that a firecracker caused the loud bang outside of Baltimore's Clarence M. Mitchell Jr. Courthouse on Thursday afternoon, prompting a bomb scare that closed downtown streets during rush hour.
Maj. Sam Cogen of the city sheriff's department said the material that caused the small explosion is being analyzed by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives but was "characteristic of a firework."
He said a more specific description was not available because authorities had not determined what specific kind of device was used.
The incident occurred around 2:30 p.m., with witnesses reporting a "boom" and seeing white smoke rising from a trash can on the sidewalk on North Calvert Street in front of the courthouse. After closing surrounding streets, officials guided a robot to the trash can to pick through its contents.
No one was injured, and damage was limited to the inside of the trash can.
Cogen said footage from surveillance cameras was being analyzed to determine whether they could develop a suspect.
"This crime is being taken very seriously, and your best course of action is to immediately turn yourselves in to law enforcement authorities," Sheriff John W. Anderson said in a statement that officials said was directed to the person who set off the firecracker.
Agents from the Department of Homeland Security and the Bureau of Alcohol, Tobacco, Firearms and Explosives also responded to the incident.
Baltimore police assisted.
The Baltimore sheriff's office, which handles security at the courthouse, took the lead in the investigation.