At least nine hoax school-shooting calls have been made to 911 in Minnesota over the past two days, according to the state's Bureau of Criminal Apprehension, which has been investigating.

All the calls appeared to come from the same person, who used a voice over IP to conduct the calls, the BCA tweeted Tuesday.

The hoax calls, also known as "swatting," came into 911 call centers in police agencies for Duluth, Ely, Eveleth, Brainerd, Bemidji, Austin, Alexandria, Crookston and Albert Lea.

The BCA has assisted local and federal agencies with investigating these incidents since they started to occur here in Minnesota and across the nation last year, according to a BCA spokesperson.

The BCA's Minnesota Fusion Center sent an alert about the hoaxes to law enforcement statewide.

Minnesota had 27 hoax school shooting calls in 2022, including 17 in September.

None of the threats were found to be legitimate, but law enforcement must treat each of them seriously, the BCA said.

The BCA implemented an app for reporting threats of school violence in the state in 2021 called See It, Say It, Send It. Students, parents and school staff can use the app to send a tip to the BCA using their cellphones or other mobile devices. The BCA then notifies law enforcement and assists with responding to any criminal activity, according to a news release.