Forensic experts believe the fire started accidentally, possibly caused by a cigarette or a lighter. The flames quickly consumed flammable materials in a storage room located on the top floor of a building on Montseny street, creating a lethal amount of smoke in a space with no ventilation.

The victims were found by firefighters in a hallway outside the storage room, suggesting they tried to flee but became disoriented by the thick smoke. Although they did not live in the building, friends reported that the group frequently used the attic as a meeting point.

The Manlleu City Council stated they were unaware of the unauthorized use of these storage units. Meanwhile, technical reports have confirmed that the building's structure remains safe, allowing residents to return to their homes following the incident.