A far-left group has claimed responsibility for the suspected act of sabotage on a Tesla factory's power supply on Tuesday , with police now confirming their message is "authentic."

"We consider the letter to be genuine, authentic," said a spokeswoman for the Brandenburg state police on Wednesday, still referring to the incident as "deliberate arson" rather than explicitly calling it an attack.

The Tesla Gigafactory in Grünheide, near Berlin, was evacuated on Tuesday, and thousands of homes were left without electricity after a major power outage for which the "Vulkangruppe" (Volcano Group) has claimed responsibility.

How has Elon Musk reacted?

Tesla owner Elon Musk on Tuesday decried the group as "the dumbest eco-terrorists on Earth." However, the left-wing extremists say their motivation was "extreme conditions of exploitation" suffered by the workforce.

Musk also spoke to the economy minister for the state of Brandenburg, who described the US entrepreneur's reaction as "objective."

"Elon Musk was very objective and assured," Jörg Steinbach told Berlin's Tagesspiegel newspaper on Wednesday. "We immediately agreed that we must not react in such a way that would hand the assailants a success."

He said Musk had expressed "solidarity" in his reaction but had also demanded "concrete, trust-building measures to support the business and its employees."

Steinbach insisted that no further consequences are to be expected provided state government and police demonstrate an "adequate response." 

What has the German government said?

On Wednesday, the German government strongly condemned such attacks on key energy infrastructure, with vice-chancellor and economy minister Robert Habeck describing it as a crime that must be investigated.

"This is by any standards wrong and not acceptable in any way," he said, adding that while protest is a democratic right, political debates should not cross a line.

"I have the feel we're approaching a juncture and must not go in the wrong direction," he said.

What is the fallout for Tesla?

US electric car manufacturer Tesla said on Wednesday that the incident has caused several hundred million euros worth of damage.

"This means economic damage in the high nine-figure range for us," said plant manager Andre Thierig, saying that costs stem from the number of vehicles that cannot be produced during the power outage and, therefore, will not be sold.

The plant manager reckoned that more than 1,000 cars per day would be lost and assumed that production would be canceled for at least this week.

The Grünheide plant is Tesla's only manufacturing plant in Europe and is where the Model Y is produced. The cars sell for between €45,000 and €60,000 ($48,900 and $65,300).

The head of the Center of Automotive Management (CAM) in the western German town of Bergisch Gladbach expressed concerns on Wednesday that the incident risked damaging foreign investors' trust in Germany as a secure manufacturing site.

Stefan Bratzel said that there were other ways of disrupting production than just cutting off power, such as blocked delivery routes and cybersecurity. He called on the state to ensure that "criminal energies are contained."

mf/dj (AFP, dpa)