An anthrax scare at the DeKalb County courthouse led to an evacuation, a quarantine and multiple federal and local agencies swarming the area Tuesday as a precaution.

A clerk’s office was evacuated “in an abundance of caution” due to a threatening letter found in the building that claimed to contain the deadly substance, according to DeKalb sheriff’s office spokeswoman Cynthia Williams.

While the incident remains under investigation, preliminary tests found no traces of anthrax in the letter, Vera Morrison, deputy chief of the Decatur Fire Rescue Department, said in a news conference.

Crowds of people were gathered in the parking lot of the courthouse and multiple firetrucks were parked outside the building while authorities investigated the incident, according to footage from Channel 2 Action News.

Williams said an employee received and opened a “suspicious letter” about 2 p.m. The note said the envelope contained anthrax.

“There was nothing in the envelope except the note,” she said. “According to protocol, the note was tested and found to be harmless.”

Some individuals who came into contact with the letter were temporarily quarantined inside the building, Williams said. Channel 2 reported there were three employees impacted by the quarantine, but decontamination was not necessary before their release. An all-clear was given about 5:30 p.m.

“We do not take these threats lightly, so we always respond as though it is the real thing,” Morrison said.

No one has been taken into custody, and the origin of the letter remains unclear, authorities said. The investigation has been taken over by the FBI, GBI and U.S. Department of Homeland Security.

West Trinity Place between Commerce Drive and Church Street was blocked near the courthouse, which is off North McDonough Street. A turnaround near Swanton Way was also closed, according to Decatur police.

Anthrax is a serious disease caused by bacteria known as bacillus anthracis, according to the Centers for Disease Control and Prevention.

—Staff writer J.D. Capelouto contributed to this article.

Channel 2?€™s Tom Jones has learned someone in the clerk?€™s office received a letter with a substance inside. A note said the substance was Anthrax.