The Chisago County Government Center opened its doors an hour and a half Tuesday night after a bomb threat was sent to election staff, County Administrator Chase Burnham said.

The threat was sent via email and was deemed not credible by the State, Burnham added. The building was searched and cleared.

The Minnesota Secretary of State’s Office said bomb threats have been sent to election offices in more than half of Minnesota counties since last week.

Burnham added that authorities are working with the state and federal government to trace the email and determine its origin.

On Tuesday, Minnesota Secretary of State Steve Simon sent the following statement regarding threats against county election offices.

“Threats of violence against election workers, intended to disrupt our democracy, are absolutely unacceptable. Although Election Day is over, election officials across the state continue their work to verify that the election was free, fair, accurate and secure. Over the next few weeks, counties will canvass the election, certify election results and conduct post-election reviews.

“Our office is coordinating with local, state and federal partners to respond and ensure our election officials can complete this important work and that those responsible for these threats are held accountable.”