A suspicious package that closed the Old Post Office Building in Washington, D.C., and forced. Washington, D.C., Metro Police to block off a four-street radius for two hours on Thursday turned out to be a dirty diaper.

Alan Etter, spokesman for the D.C. Fire Department, said two other incidents of dirty diapers also stopped activities at two other high-profile buildings in the city during the day, but he could not provide details. A Metro Police spokesman said he was not aware of any other instances involving poopy pants.

The streets around the Old Post Office Building, which houses the Smithsonian's National Postal Museum, were shut down beginning just after 11:30 a.m. ET. Police captain J.L. Brown told FOX News that a post office official called the police, who arrived within minutes with an explosives team and a hazardous materials team from the fire department.

After an initial negative chemical reading, the hazmat team put the suspicious package into the X-ray to determine what was inside. Upon closer examination, the crews discovered that the suspicious odor was from the fouled diaper left in a box on the post office counter.

FOX News' Caroline Shively, Justin Fishel and Jodie Curtis contributed to this report.