The outage on Saturday affecting about 45,000 households and more than 2200 businesses was the result of a politically motivated attack, according to Wegner, who is a member of the Christian Democrats (CDU) led by Chancellor Friedrich Merz.
"It is unacceptable that left-wing extremists are once again attacking our power grid and endangering human lives," said Wegner, referring to a similar attack on two power pylons in the city in September.
A lengthy document posted online from the alleged perpetrators claiming responsibility in the current case was titled "Cutting off the Power to the Rulers".
"In the greed for energy, the earth is drained, sucked dry, burnt, abused, burnt down, raped destroyed," it stated.
The gas power plant in Berlin-Lichterfelde was "successfully sabotaged," it said.
"Power outages were not the target of the action but rather the fossil energy industry," the group claimed in the letter.
Early on Saturday morning, a fire on a cable bridge over the Teltow Canal to a power station damaged several key power lines, affecting the city's Nikolassee, Zehlendorf, Wannsee and Lichterfelde districts.
The outage hit street lighting, mobile telecoms, traffic lights and supermarket fridges as well as private households, shutting down heating systems as temperatures hovered at freezing point.
Police began investigating a suspected arson attack after the state security service responsible for political crimes received a letter claiming responsibility.
The letter is authentic, Interior Senator Iris Spranger told the DPA news agency on Sunday.
The electricity provider reconnected many homes overnight but said it will not be possible to restore power to all affected households until Thursday afternoon.
September's outage also persisted for several days.
"By 3.23am on 4 January, we had been able to restore power to about 7000 households and 150 businesses in several stages, particularly in the Lichterfelde area," Stromnetz Berlin said on its website.
Affected businesses are expecting serious economic consequences due to the power outage.
"We anticipate millions in damages to equipment and machinery and high losses in revenue," said Alexander Schirp, chief executive of the Berlin and Brandenburg Business Association (UVB).
The situation is placing extreme strain on companies and shows the need for better protection for sensitive equipment, Schirp said: "The power outage shows that our infrastructure is not adequately protected against attacks and accidents."
According to Berlin's Senator for Economic Affairs Franziska Giffey, incendiary devices had been placed directly under the cables.
"The force with which continuous heat development and a continuous fire occurred was greater than the force that a 'ball shell' (an explosive pyrotechnic) could have triggered," Giffey told local broadcaster RBB on Saturday evening.
"A 'ball shell' would not have been able to damage our cables, given how they are secured," she added.
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