San Francisco-headquartered Hornblower Group has shut down its US river and expedition cruise arm, American Queen Voyages, putting the company under Chapter 11 bankruptcy protection ahead of the liquidation of its assets.

American Queen Voyages, which operates four river cruise ships and four expedition cruise vessels sent all its ships to the wall on Thursday, cancelling all future cruises.

The company also informed all staff and crew that their employment was terminated with immediate effect.