Elon Musk has said a suspected arson attack which has halted production at Tesla’s Berlin car factory was “dumb”.
A far-left activist group says it targeted the site because of the amount of resources and labour it uses.
The company says car-making is unlikely to resume before next week, with the outage likely to cost it “in the high nine-digit euro range.”
Tesla wants to double the size of its German factory – a plan which is opposed by some environmentalists.
In a post on X, formerly Twitter, Mr Musk used the German phrase “extrem dumm” – extremely stupid – to describe the targeting of the site.
“These are either the dumbest eco-terrorists on Earth or they’re puppets of those who don’t have good environmental goals,” he wrote.
In a letter published online, activists calling themselves the Volcano Group said they sabotaged production.
An electricity pylon close to the plant caught fire, causing power outages in the factory and nearby towns.
Tesla said workers had been sent home but its building was in a “safe state”.
The fire did not reach the electric car-maker’s factory itself but did burn an electricity pylon and high-voltage wires.
In its letter claiming responsibility for the attack, the Volcano Group said it sabotaged Tesla because it ate up resources and labour.
It also accused Tesla of contaminating groundwater and using huge amounts of drinking water.
State police have told the BBC they are currently examining the letter.
“The rule of law will react to such an act of sabotage with the utmost severity,” said Interior Minister for Brandenburg state Michael Stuebgen after the attack took place on Tuesday morning.
Controversial expansion
Some environmentalists are unhappy with the Berlin expansion plan because it would involve chopping down nearby trees.
Around 100 people are camping in a forest near the factory. However, those green activists have distanced themselves from what has happened.
One group, which calls itself Robin Wood, told the BBC it had “nothing to do with the fire”.
The Tesla factory currently makes around 500,000 cars a year – the Elon Musk-owned company wants to double that.
Production is not expected to restart until next week, according to plant manager Andre Thierig.
He added that the outage would cost “in the high nine-digit Euro range” after both power lines into the plant were broken.