A mock cannon on a Greek tour boat exploded Saturday, killing the captain and injuring six tourists off the island of Kos, authorities said.

The Merchant Marine Ministry said the tourists from Germany, Belgium, Greece and the Netherlands — including two children, aged 7 and 9 — were hospitalized on the east Aegean Sea island with minor injuries. Twenty two other passengers on board all disembarked unharmed at the island port of Mandraki.

The extent of damage caused by the explosion remained unclear. The ministry said the wooden boat was used for excursions around the island and had been fitted with the mock cannon to resemble a small pirate ship. It wasn't immediately clear if gunpowder was used to simulate cannon fire.