The police immediately started an investigation after the fire. They secured camera footage and took multiple witness statements. This investigation revealed that a group of youths had taken several emergency flares and a so-called fire axe from a ship prior to the fire. There are strong indications that the use of a so-called flare was the cause of the fire. Strict safety regulations apply to the use of such emergency flares.

On Wednesday, July 16, 2025, two suspects were arrested in the early morning. Later that day, two more suspects reported themselves. A fifth suspect was arrested that same evening. All suspects are minor boys aged 15 to 17 from Rotterdam.

One suspect has since been released pending trial. At least four boys are being prosecuted.