HALIFAX, Nova Scotia (AP) _ Two luxury cruise ships operated by a U.S. company were seized by harbor authorities Thursday, and at least 850 passengers were put ashore, officials said.

The Rembrandt and the SeaBreeze are owned by Premier Cruise Lines of Port Canaveral, Fla. It couldn't be immediately confirmed why authorities took control of the vessels. Canadian Press, Canada's news agency, reported that unpaid bills were the apparent reasons.

The passengers were aboard the 15,000-ton Rembrandt, officials said. They were directed to clear out their belongings and walk to the pier.

``Last night was pirates theme night (on the ship),'' said a female passenger, who declined to give her name. ``Today, we're walking the plank.''

In Boston, Massachusetts Port Authority official Georgeane Tacelie, who confirmed that the SeaBreeze had been seized, said Premier Cruise Lines notified the port that it had ceased operations Thursday. Tacelie said that the move left the Boston-bound cruise ship stranded in Halifax. It wasn't immediately known how many passengers, if any, were aboard the Seabreeze.

By the afternoon, some of the Rembrandt passengers had left Halifax by bus.

Halifax harbor master Randy Sherman said some of the passengers would remain overnight aboard other ships in the harbor.

``We're just hoping the passengers would be accommodated on the ships and it's my understanding they'll be flying home tomorrow,'' Sherman said,

The Rembrandt, which can carry 1,074 passengers, began its cruise in New York.

Calls to the cruise line were going unanswered Thursday evening. A recorded message said: ``Thank you for calling Premier Cruise Lines. Our office is temporarily closed due to a facility problem.''

Premier Cruise Lines has made regular stops in Halifax harbor for several years.

``They're one of our most frequent callers and we've always had good business with them,'' said Sherman, who estimates the line has been in port 40 or 50 times.