But Atlanta Police said it was a Georgia State University student's art project attached to the outer frame of the 14th Street Bridge in downtown Atlanta that shut down all north and southbound lanes of Interstate 75/85 for two hours on Monday.
"Georgia State has taken responsibility for the object," Assistant Chief Shawn Jones said at a news conference Tuesday.
The department said it received a 911 call regarding a suspicious package around 12:50 p.m. Monday. When crews went to investigate, they "found an object that looked like an explosive," Jones said.
Jones wouldn't describe what the object in question looked like, but a photo gallery
obtained exclusively by CNN affiliate WSB, showed a soda can covered in duct tape.
Police moved to shut down all lanes of traffic to "conduct controlled disruption to render it safe," Jones said. The results were eerie scenes of a usually bustling thoroughfare left empty.
No explosives were found and all lanes of interstate traffic reopened shortly after 4 p.m.
Georgia State announced Tuesday that an art project was to blame.
"Georgia State University sincerely apologizes for the traffic problems resulting yesterday from the mounting of a student camera at the 14th Street Bridge," Don Hale with university media relations said in a release.
No one from the Atlanta Police Department or the Department of Transportation was made aware of the 18 cameras deployed at various locations in the city, Jones said.
Photos of other cameras show them attached to trees, fences and windows around the city. Some include notes that identify the soda can as a "Georgia State Art Project." Some instruct passersby to "Please do not take down!"
Police are working with the school to remove all the cameras, the university release said.
Jones said the incident is still under investigation and it has yet to be determined if charges will be filed.