The Denver Post Police said someone fired a shot at an Obama campaign field office in Denver yesterday.
No one was injured, though people were inside the office when the incident occurred, said Denver police spokeswoman Raquel Lopez.
"It looks like it was one shot that was fired into the structure," she said.
The incident happened at the campaign's office on West Ninth Avenue near Acoma Street, Ms Lopez said.
Sam Levin, a reporter for the newspaper Westword, later posted a photo on Twitter showing one of the office's large front windows broken out.
By early evening, the window shards had been removed and a glass company was putting up plywood.
Ms Lopez said police have a description of a "possible vehicle of interest."
She said she could not release that information while detectives are reviewing any available video footage of the incident and pursuing leads.
An Obama campaign spokeswoman declined to comment on the incident, instead referring a question to the police.
New York Times