GRAND RAPIDS, Mich. (AP) — Authorities have reopened a western Michigan courthouse after locking it down while they investigated a suspicious package.

The Kent County Sheriff's Office says the 63rd District Court in Grand Rapids was locked down for about three hours Monday while deputies, the FBI and the Grand Rapids Fire Department Hazmat Team investigated an envelope that arrived in the mail containing a powdery substance.

It says the courthouse was reopened about 1 p.m. once investigators determined the substance had been contained and didn't pose a threat to anyone inside or outside of the building.

The sheriff's office says additional testing will be conducted to determine what the substance is.

It says no symptoms of exposure have been reported.