EAST CHICAGO, Ind. (WDRB) -- A postal worker is hurt in an explosion at a northern Indiana post office.

The FBI is investigating but hasn't determined whether the blast on Wednesday night was an act of terrorism. 

The explosion is believed to have been caused by a pipe bomb that was inside a package. The incident happened around 6 p.m. in East Chicago, Indiana. 

The bomb squad and K-9 units responded to the scene. One unidentified witness was shocked by what happened, "Oh, my god.  This is crazy. Is this terrorist or what?  Especially with helicopters hovering over.  And now more squad cars coming so, it's kinda scary."

There is no word yet on where the package may have come from.

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