Authorities evacuated a St. Louis County courthouse Wednesday afternoon after receiving a bomb threat but did not find an explosive inside the building, according to deputies.

The county’s 911 dispatch received a call just before 12:30 p.m. Wednesday from someone saying a bomb was inside the district courthouse in Virginia, Minn.

St. Louis County Sheriff deputies, courthouse security and a bomb-detecting dog from the Duluth Police Department cleared the building. They did not find any explosive after an “extensive search,” according to the Sheriff’s Office.

The Sheriff’s Office is investigating the incident.