An envelope containing a powdery substance was discovered by an employee at the federal courthouse in Boston this afternoon, the Boston Fire Department said.

A hazardous materials response team was summoned to examine the envelope around 3 p.m. A field test of the substance and surrounding air was conducted and the results were negative, the department said in an official tweet.

The substance was then transported to the state laboratory for further tests. The FBI is investigating the incident, the fire department said.

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No injuries were reported.