A passerby reportedly discovered the object in the town of Dormagen, between Cologne and Düsseldorf, and alerted police, regional Westdeutscher Rundfunk (WDR) reports.
So far, no injuries have been reported. It is also unclear whether the object had the capacity to cause any damage, police spokesperson Claudia Suthor told WDR.
On Monday evening, a power outage occurred at a substation in Bergheim, about 30 kilometres from Dormagen. Cables had been laid on top of the power lines to cause a short circuit.
On Tuesday, a similar incident occurred on the other side of the country. Several explosive devices were found at a substation in the eastern state of Brandenburg. The station is connected to Jänschwalde, one of Germany's largest coal-fired power plants.
On Wednesday, German police announced that it was being investigated as a possible terrorist crime.
