There were reports of a possible shooter on the University of Michigan Ann Arbor campus, but the Washtenaw County Sheriff's Office said the reports were caused by residents popping balloons.

Authorities told ClickOnDetroit that the false alarm was triggered after a group of teenagers were popping balloons on State Street.

From Washtenaw County Sheriff: A group of 14 girls were popping balloons while screaming at or near Mason Hall. A group of students heard this and started running. This triggered the alert on campus. Police have given the all-clear. — Steve Garagiola (@SteveGaragiola) March 16, 2019

The university issued a "Run Hide Fight" warning at 4:55 p.m. local time, for anyone in or near Mason Hall. The university asks students and staff to try to remain calm during an emergency and wait for an "all clear" sign before resuming normal activities.

ALL CLEAR.. no active shooter at U of M after all. Unconfirmed reports of kids with balloons. Newschannel 3, CBS News, WWMT, West Michigan — WWMT Andy Dominianni (@WWMTAndyD) March 16, 2019

Ann Arbor Police told WDIV they were searching Mason Hall and have yet to find evidence of an active shooter. However, they took the threat "very seriously" and were investigating because of a report of that being a possibility.

After the alert was tweeted, university staff tweeted, "Unconfirmed reports of active shooter, Officers are in the area checking. Stay away from the area of Mason Hall."

Unconfirmed reports of active shooter, Officers are in the area checking. Stay away from the area of Mason Hall. https://t.co/hXZESJocIO — University of Michigan (@UMich) March 16, 2019

At 5:34 p.m., the university tweeted that there "does not appear to be an active threat to the community."

UM ALERT UPDATE There does not appear to be an active threat to the community. DPSS continues to investigate. Continue to stay clear of area. https://t.co/BRDwV3MOmd — University of Michigan (@UMich) March 16, 2019

According to ClickOnDetroit, there were also reports the Bell Tower Hotel was placed on lockdown.

UM EAlert Ann Arbor: Active shooter in Mason Hall . Run, hide, fight. https://t.co/NofE7JP8yS. https://t.co/03ZOte5ylP — University of Michigan (@UMich) March 16, 2019

A person at campus police answered the phone and said the building was being searched, reports the Detroit Free Press.

Active shooter in Mason hall now pic.twitter.com/eSDIybL9Pa — Max Kuang (@KuangMax7) March 16, 2019

A photo sent to The Daily from a student in a university library: pic.twitter.com/oTgnPdvouw — The Michigan Daily (@michigandaily) March 16, 2019

The Michigan Daily reports that police were receiving calls of a shooter "heading towards" the undergraduate library, but "nobody has been spotted."

Police also started removing students from Mason Hall as they searched the floors.

Photo credit: University of Michigan