"Multiple vessels... were illegally intercepted and boarded by Israeli Occupation Forces in international waters," the organisers said in a statement.
Our vessels are being illegally intercepted. Cameras are offline and vessels have been boarded by military personnel. We are actively working to confirm the safety and status of all participants on board.
On Tuesday night video footage emerged of the Alma - which Mr Hickey was onboard at the time during night watch - was set ablaze after a device was dropped on its top deck from a flying apparatus, suspected to be a drone. Activists supplied the Irish Independent with a photograph showing the charred device they say dropped onto the Alma's deck.
