Russia is building power lines in occupied southeastern Ukraine to link to its own grid a major nuclear plant it has captured, according to a new Greenpeace report. It is the clearest evidence yet of Moscow’s intent to restart and exploit the offline facility, despite the risks and calls to address the plant’s status in peace talks.

The facility, the Zaporizhzhia nuclear power plant, was seized by Russia early in the war in a move widely condemned by the international community. Its proximity to frontline fighting has raised fears of a potential nuclear disaster, and experts have warned against any attempt to restart the plant under current conditions.

The Greenpeace report, which was shared with The New York Times, includes satellite images showing that, since early February, Russia has been building more than 50 miles of electricity lines and pylons between the occupied Ukrainian cities of Mariupol and Berdyansk, along the coast of the Azov Sea. The satellite images were verified by The Times.

Based on the location and direction of the work, Greenpeace said the project aimed to link the new power lines to a large substation near Mariupol that was connected to the Zaporizhzhia nuclear plant, about 140 miles farther west.

“Putin’s plan for restarting the Zaporizhzhia nuclear plant depends on securing new electricity transmission lines — this is the first physical evidence of those plans,” Shaun Burnie, a nuclear specialist at Greenpeace Ukraine, said in an interview.

Moscow’s exact plans remain unclear. There are questions about whether it seeks to run the plant in a postwar Ukraine or to do so while fighting is still underway. In either case, experts note, Russia would need to build several more lines to connect the Zaporizhzhia plant to its own grid, a process that would take time.