Potsdam police said it was too soon who may have been responsible.
German media said it was delivered to a pharmacy on Friday afternoon. They later tweeted that the device had been defused. Hours later, however, Interior minister of Brandenburg, Karl-Heinz Schroeter, reported that y had found nails inside a suspect metal container as well as a white powder, but that y should still determine if re were also explosive substances.
Authorities on Friday defused an explosive device found near an outdoor Christmas market in the German city of Potsdam, near Berlin, Reuters reported.
The police said earlier on Twitter that "the suspicion of an improvised explosive device has been confirmed".
"We are now carrying out searches because the package was delivered, apparently, and possibly other packages had been delivered nearby the Christmas market".
Potsdam police said they cleared the area around where the object was found and were investigating.
Police warn that there may be more such packages in the area.
In December 2016, 12 people were killed at a Christmas market in Berlin - just 18 miles from Potsdam - when a lorry was hijacked and driven into crowds in an attack which was later claimed by so-called Islamic State. The suspect, Anis Amri, fled to Italy after the December 19 attack and died in a shootout with police near Milan on December 23, 2016.
Security has been stepped up at all markets across Germany ahead of that anniversary, and the looming first Advent weekend.