HAMMOND, Ind. (AP) — A northwestern Indiana man has been arrested on federal charges in connection with a pipe bomb that exploded last month at a post office.

U.S. Attorney Thomas Kirsch II announced Thursday that 45-year-old that Eric P. Krieg of Munster, Indiana, was charged with knowing possession of a destructive device and transporting explosive materials. Kirsch says a complaint alleges Krieg mailed a package at the East Chicago post office that exploded and that he mailed a suspicious package to another individual on Sept. 29.

Kirsch says search warrants were executed Thursday on Krieg’s residence, place of employment and vehicle.

A postal worker suffered minor injuries in the explosion.

It wasn’t immediately clear if Krieg has an attorney.