LAS VEGAS (KLAS) — Two inmates at Ely State Prison sent mail containing a “powdery substance” to a Las Vegas courthouse, according to the Nevada Department of Corrections.

The mail was delivered on Friday and Monday. The substance in one envelope was identified as harmless, and the other substance has not been identified, NDOC said.

The incident is under investigation, and no injuries or symptoms have been reported.

Legal mail and correspondence sent by inmates are not searched before leaving NDOC facilities, according to administrative regulation. Mail that is addressed to the governor, the attorney general, or the secretary of state is inspected by NDOC staff before being sealed and sent.

“While the investigation into this incident is ongoing, NDOC will begin to review regulations and procedures for best practices going forward,” a statement from the department said.