ST. PAUL, Minn. (AP) — The FBI and the U.S. Postal Inspection Service on Friday were investigating the origin of a suspicious package that was sent to the Minnesota Secretary of State’s Office, prompting an hourslong evacuation.

Friday’s episode in Minnesota was the latest in a string of suspicious package deliveries to elections officials in more than 15 states earlier this month. The Minnesota Secretary of State’s Office in St. Paul was evacuated around noon on Friday, and the building remained under lockdown into the afternoon, said Cassondra Knudson, a spokesperson for the office.

The package was addressed to the office with a return address to the “United States Traitor Elimination Army,” the office said in a news release. That matches the sender of a package to the Colorado Secretary of State’s Office earlier this month. Minnesota Secretary of State Steve Simon said his office would work with law enforcement agencies to hold whoever sent the package accountable.

“Threatening election officials is unacceptable and cannot be tolerated,” Simon said in a written statement. “Our democracy depends on public servants who must be able to perform their duties free from fear, intimidation, or harassment. This action is not deterring our work or determination to deliver another election that is free, fair, accurate, and secure.”

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In Minnesota on Friday and in the earlier episodes in other states, there were no immediate reports of injuries or that any of the packages contained hazardous material.

The earlier packages were sent to elections officials or intercepted before they arrived in Alaska, Colorado, Georgia, Indiana, Kentucky, Massachusetts, Missouri, New York, Rhode Island, Mississippi and Connecticut.

The FBI said those packages contained “an unknown substance” but did not offer further details. The agency declined to offer additional information about the status of the investigation or the specific threat in Minnesota on Friday.

The latest scare comes as early voting has begun in several states ahead of the high-stakes elections for president, U.S. Senate, Congress and key statehouse offices, disrupting an already tense voting season. Local elections directors are beefing up security to keep workers and polling places safe while also ensuring that ballots and voting procedures won’t be tampered with.

The National Association of Secretaries of State condemned what it described as a “disturbing trend” of threats to election workers leading up to Nov. 5, as well as the second apparent assassination attempt on former President Donald Trump.