The bomb used to kill Maltese anti-corruption blogger Daphne Caruana Galizia was probably triggered by a call from a boat off Malta, an investigator said on Tuesday, laying out initial evidence against three suspects.

Caruana Galizia died in the powerful blast as she was driving near her home in the village of Bidnija on Oct. 16 — a killing that appalled Europe and raised questions about the rule of law on the tiny Mediterranean island.

Brothers Alfred and George Degiorgio, and Vince Muscat were arrested earlier this month in connection with the murder. The three men, who were known to police, have denied any wrongdoing.