German police reported a third suspected sabotage attempt on a power grid this week after a suspicious object was discovered at an electrical substation in the western city of Dormagen, local media reported Friday.
"Someone apparently tried to deliberately cause a short circuit," a Cologne police spokesperson said early Friday.
Investigators received a letter claiming responsibility that also mentioned other publicly known suspected cases in North Rhine-Westphalia and Brandenburg, private broadcaster n-tv reported, citing the police spokesperson.
The investigation into the suspicious object, which a passerby discovered Thursday evening at the electrical substation in Dormagen, has not been completed.
It may be a "suspicious launching device," the spokesperson said.
Police are also checking substations in surrounding areas for suspicious objects.
So far, no damage has been detected except at an electrical substation in Bergheim, near Cologne.
Authorities earlier said cables were placed across overhead power lines at the Bergheim substation Tuesday, causing a short circuit.
Several launching devices were discovered afterward, according to the authorities.
A similar incident also occurred Tuesday in the eastern state of Brandenburg. Unidentified suspects carried out a sabotage attack on an electrical facility at a major power plant in Jaenschwalde, authorities said.
Brandenburg Interior Minister Jan Redmann told reporters that the suspects used projectile devices to cause a short circuit in an extra-high-voltage line near the plant.
Investigators said they believe the incidents in Bergheim and Jaenschwalde were acts of sabotage.
