An envelope ignited at a post office in Washington, Reuters reports.
According to reports, a mail sorter was throwing mail into a bin, when the package ignited on its own, and she smelled smoke.
Officials said the letter was addressed to Homeland Security Secretary Janet Napolitano, according to Reuters.
The building has been evacuated police said, but no-one was injured.
The incident comes a day after two similar explosions at Maryland buildings, but officials can’t say yet if this incident is related.
The facility in which this latest incident happened was built after the 2001 anthrax attacks to screen mail headed for federal office, CNN reports.
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