The owner of La Luna, the yacht at the centre of the fatal incident in Cala Bona on Friday night, faces possible arrest for manslaughter and failure to provide assistance.
It was initially believed that there had been a tragic and unfortunate accident without criminal implications, but the Guardia Civil investigation has since been transferred from the force's maritime service to the homicide squad.
Questioning of crew members on Monday covered episodes that had occurred some hours earlier last Friday. Around a dozen passengers were holding a party on the yacht in the area of Cala Agulla. There were complaints about behaviour and the apparently reckless high-speed use of a small auxiliary vessel.
At dusk the yacht left Cala Agulla and headed for Porto Cristo. It was travelling at high speed when it struck the fishing boat off Cala Bona; 20-year-old Guillem Comamala was killed. The fishing boat didn't have lights.
People on board La Luna are understood to have told investigators that they weren't aware of what had happened. Sources suggest that it would have been "practically impossible" not to have noticed the collision.
The owner of the yacht is said to be a German millionaire.