FARGO (AP) - Authorities say a suspicious white substance found in an envelope at a US Bank processing center in Fargo was wheat flour.

Employees at the center in Fargo were not allowed to enter or leave the building for more than an hour on Tuesday while authorities checked out the envelope.

Authorities say an employee had opened an envelope and white powder spilled out.

Fargo fire, police and hazardous materials officials responded.

Police Lt. Pat Clause says the case has been turned over to the FBI.

Fargo Fire Marshal Norm Scott says is a return address on the envelope, but it has not been released to the public. He says authorities are trying to contact someone at that address.