Swedish police have concluded their investigation into the deaths of four Northvolt employees in Skellefteå, determining that no hazardous substances were involved.

The probe began after three workers died following their shifts at the battery factory.

Despite extensive analyses, the cause of these deaths remains unclear, though natural causes such as illness are suspected.

A fourth death, unrelated to the workplace, was ruled a drowning accident.

Northvolt representatives and union officials expressed relief at the findings, which dispel fears of workplace chemical exposure.

The case is now closed, with no criminal activity suspected.