Denver police are investigating reports of gunfire directed toward a campaign field office for President Barack Obama’s re-election campaign Friday.

According to The Denver Post, there were people inside the office when a shot was fired at the building, but no one was injured.

Police told KCNC-TV they do not know whether the shot was fired intentionally, or whether it was a stray bullet.

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Sam Levin, a reporter for the alternative newspaper Westword, posted a picture on Twitter showing one of the large windows at the front of the building had been shattered.

“I have zero details about what happened here,” Levin wrote. “But Obama 9th and Acoma campaign headquarters window badly smashed.”

Authorities said they are reviewing possible video footage of the incident, and have a “possible vehicle of interest.”

An Obama campaign spokesperson refused to comment on the incident.

[Image via Sam Levin on Twitter]