Wrapped brick. Wrapped in brown paper; posted in street corner box with same amount of postage as was strapped to unwrapped brick. Extreme weight for size made package seem suspicious. Notice of attempted delivery received, 16 days. Upon pickup at station, our mailing specialist received a plastic bag containing broken and pulverized remnants of brick. Inside was a small piece of paper with a number code on it. Our research indicates that this was some type of US Drug Enforcement Agency release slip. The clerk made our mailing specialist sign a form for receipt.