BERLIN — Production at Tesla's electric vehicle plant near Berlin came to a standstill and workers were evacuated on Tuesday after a power outage that officials suspect was caused by arson. Elon Musk, who is Tesla's CEO, condemned the incident.

The interior ministry in the state of Brandenburg, where the plant is located, said unidentified people are suspected of deliberately setting fire to a high-voltage transmission line on a power pylon. The state criminal investigation department began an investigation into the fire.

Police said they have been made aware of an emailed claim of responsibility, which they were examining, German news agency dpa reported.

The report said a far-left group called “Volcano Group” said it was behind the fire, accused Tesla in the email of “extreme exploitation conditions” and called for the “complete destruction of the gigafactory.” It was not immediately clear who the email was sent to or who was behind the group.

Referring to the possible attackers, Musk, who owns about 13% of the Tesla stock, wrote on X, formerly Twitter, that “these are either the dumbest eco-terrorists on Earth or they’re puppets of those who don’t have good environmental goals.”

“Stopping production of electric vehicles, rather than fossil fuel vehicles, ist extrem dumm,” he added, using the German words for “extremely stupid.”

The power outage comes as environmental activists have been staging a protest in a forest near the plant against plans by Tesla to expand.

In the “Stop Tesla” protest, dozens of activists have put up tents and built treehouses, some of them several meters (yards) above the ground, a tactic used in previous German environmental protests.

The early morning fire caused power to fail in surrounding towns, including Grünheide, where the Tesla factory is located. Electricity was restored after a few hours in the nearby towns and villages, but Tesla remained without it in the early afternoon.

Tesla opened the factory in March 2022, launching a challenge to German automakers on their home turf.

The company now wants to expand the facility to add a freight depot, warehouses and a company kindergarten. Those plans would entail felling more than 100 hectares of forest.

That has drawn opposition from environmentalists and some other local groups, which also worry about the possible effect on the area’s water supply. In a nonbinding vote in mid-February, residents of the municipality rejected Tesla’s plans, which still need approval by local authorities.

About 12,500 people work at the plant.

Brandenburg Gov. Dietmar Woidke condemned the alleged attack.

“This is obviously a serious attack on our critical infrastructure with consequences for thousands of people and many small and large companies in our state,” he said. “Attacks on our critical infrastructure are a form of terrorism.”