An anthrax scare, which eventually proved to be a hoax, closed the Linn County Courthouse on Monday.

Early in the morning, a janitor found threats written on the outside door, warning there were some envelopes containing anthrax inside the courthouse and in the nearby area. Local media sources informed that the note said there were 10 envelopes inside the building.

“The note indicated that anthrax was in envelopes in the courthouse,” Linn County Sheriff Tim Mueller said.

Other notes said “Don’t touch the letter you’ll be sorry” or “This is not a joke.”

Only one clerk was inside the building at the time and he was evacuated. All the 29 court hearings were cancelled. The building was then shut down so that members of the FBI, Department of Homeland Security, Oregon Army National Guard, the Linn-Benton Region 5 Haz-Mat team and the Linn County sheriff could investigate whether the threatens represented a real danger.

The search revealed only two envelopes, of which one had been left with the note outside and one had been slipped under one of the doors.

After taking the envelopes to a mobile testing center and analyzing them thoroughly, the investigators found out that the substance was definitely not anthrax, but only something similar to granulated white sugar. A sample of the substance was still taken to the FBI laboratory in Portland for further investigation.

Authorities have found no suspect so far, but a criminal investigation is underway.

The courthouse is due to open on Tuesday.