BERLIN (AP) — Two incidents that disrupted power distribution systems in the west and east of Germany are being investigated as possible sabotage, authorities said Wednesday.

Multiple explosive devices were found Tuesday morning at a substation near the Jänschwalde coal-fired power plant in Brandenburg in northeast Germany. No general power outage resulted, but a few of the devices caused short circuits, authorities said Wednesday.

Separately, a short circuit that caused several power lines to go out of service Tuesday evening at the Bergheim power substation near Cologne in western Germany was a deliberate act, security officials said Wednesday, adding there was no general power outage.

RWE, the company operating coal power plants that utilize the Bergheim substation, said five coal-fired units with a combined capacity of 4,200 megawatts were taken offline after the incident.

“It wasn’t a broken switch, it was intentional. It was a criminal act,” said Herbert Reul, the interior minister of North Rhine-Westphalia state, where Bergheim is located. “We are investigating two possibilities: sabotage directed by a foreign government and left-wing extremism. We cannot rule out either possibility at this time.”

“There were bright flashes of light visible along the power lines, the overhead wires. In German, that’s called a short circuit. Several lines were affected,” Reul told reporters Tuesday night.

He added that based on the investigation’s current status, “the perpetrators deliberately caused a short circuit by placing conductive material — presumably cables — over the overhead line.”

Security officials from both regions were in contact and closely checking for possible connections between the Brandenburg and Bergheim incidents, Reul said.

“Is this connected to Brandenburg, to the attacks on the railways, to hybrid threats from abroad?” Reul said in response to a question. “The answer is: We are investigating, and very thoroughly at that. But investigating is not the same as knowing, and speculation is not proof.”

Three power plants are expected to go back online later on Wednesday. Work is underway to bring the two remaining power plant units back online by the weekend.

German power infrastructure has previously been affected under similar circumstances. Suspected left-wing extremists set fire to high-voltage lines near a power plant in southwest Berlin in January.

The country is also on high alert after the German government on Tuesday blamed Russia for an attempted attack at Leipzig/Halle Airport on Aug. 4 using a drone laden with explosives.