At around 10:40 a.m. today a 911 caller reported someone with a weapon in a building in the 0-100 block of East Street.
"As a precaution, the Sault Ste. Marie Public Library and the Art Gallery of Algoma were placed on lock down for a short time," police said by email.
Officers secured the area, then located and arrested one person.
No physical injuries have been reported.
The lock down was lifted at around noon.
Police have not confirmed if the person was found with a weapon nor what they were charged with.
Further details will be released as they become available.