The Greek authorities detained 13 members of a yacht crew on suspicion of arson, after a fire broke out and amid the heightened danger of wildfires during the summer.
The crew allegedly set off the fireworks off the coast of the popular holiday island of Hydra to entertain the guests, but sparks set fire to the island's only pine forest.
The suspects first tried to extinguish the flames then called the fire brigade and left the area.
People on other boats saw the incident and reported it to the authorities, Greek media reported, citing the coastguard. Those detained will be brought to justice, the fire brigade said.
The island's mayor expressed fury in a television interview, saying no matter what the central authorities do, the island community would also press charges against those involved.
The fire brigade brought the fire under control late on Saturday evening, aided by helicopters.
The penalties for deliberate or negligent arson were significantly increased last year in Greece, which battles repeatedly with wild fires. Alongside fines running to tens of thousands of euros, people can also receive prison sentences of up to 10 years if found guilty even of negligent arson.
Meanwhile the risk of forest fires remains high in several parts of central Greece throughout the weekend, according to the Greek Civil Defence. However, a spokesman for the fire brigade on Sunday morning said most fires had been brought under control.