At 2 pm on Thursday, a large part of Eskilstuna's central parts suddenly turned black.
The power outage lasted for just over a quarter of an hour before a backup transformer could be connected.
The disruption in the electricity grid was so severe that it was even noticed in Västerås, where a so-called block triggered at Arosverket.
During Friday, the backup solution was still in operation while Eskilstuna enerig and the environment sought answers to what may have happened.
Since Vattenfall's network was also affected, they sent up a drone to search for the power lines.
At the time of writing, it is unclear whether the error occurred at Eskilstuna energy and environment or at Vattenfall.
In the clip, Anna-Åsa Hellström, business area manager for electricity grids at ESEM, tells us what happened and what is now being done to resolve the problem. You also see Vattenfall using its drone in the hunt for electrical faults.