(CNN) A mass brawl broke out on a British cruise ship Friday morning, leaving several people injured and others confined to their cabins for the rest of their journey, according to eyewitnesses who spoke to CNN affiliate ITV news.

The P&O cruise ship Britannia was on the final leg of a cruise to Norway's fjords from Southampton, in southeast England, when the fracas broke out, ITV reported.

ITV's "Good Morning Britain" correspondent Richard Gaisford was on board the ship when the fight broke out. In a series of messages on Twitter, he said that heavy amounts of alcohol contributed to violence that started on the 16th floor restaurant on Thursday, when a passenger appeared dressed as a clown.

The passenger's attire apparently upset some of the guests, Gaisford said.

"One witness, part of a group involved in the trouble, explained to staff that things kicked off when another passenger appeared dressed as a clown," Gaisford said.

"This upset one of their party because they'd specifically booked a cruise with no fancy dress. It led to a violent confrontation."

In the United Kingdom, fancy dress means wearing a costume.

"There was blood everywhere," Gaisford wrote. "Passengers used furniture and plates as weapons. Witnesses told me they were so frightened they had to hide as family groups fought," Gaisford added.

Police told ITV that three men and three women were assaulted during the fight and that there were a number of injuries including cuts and bruises.

Those believed to have been involved in the fight were confined to their cabin for the last day of the cruise, ITV reported.

Hampshire Police told CNN on Sunday that a man and woman arrested on suspicion of assault in connection to the brawl have not been charged and were released from custody -- but remain under investigation.

In a statement, a P&O Cruises spokesman told CNN on Sunday: "Following an incident on board Britannia on Thursday evening we can confirm that all guests disembarked yesterday and the matter is now in the hands of the local police."

He added that the cruise line does not tolerate disruptive behavior.