Capitol scare triggered by DC homeless encampment fire; threat cleared. The U.S. Capitol Building was placed in a brief lockdown in response to what announcements on the grounds described as an "external security threat," Fox News has learned. The threat appears to have been linked to an outdoor fire at a homeless encampment that has since been extinguished.  The encampment was located approximately one mile away, where a plume of smoke created security concerns. Washington, D.C. Fire and EMS said the fire "accounts for smoke that many have seen."  Check out the link to read more about this.