Napolitano target of 'fire package'
The package at the Washington facility ignited a day after similar packages that were sent to the governor and transportation secretary of the nearby state of Maryland burned the fingers of workers who opened them.
Initial information indicates all the parcels are similar. The Washington postal facility was evacuated and no injuries were reported.
Security officials said the incident, and two similar incidents in the neighbouring state of Maryland this week, are not believed to be the result of Islamist terrorism.