ABC News reported that health officials from the Centers for Disease Control and Prevention boarded Silversea Cruises’ Silver Shadow while it was at port in Alaska.

The CDC found 21 discrepancies while on board, giving the ship an unsatisfactory grade of 82. It was reported that cruise staff participated in an organized effort to hide trays of food from the health inspectors.

“Since the preliminary report was given to us, a full investigation has been carried out into the circumstances which led to this unsatisfactory result and a number of steps have been taken to ensure that the standards of food hygiene, in particular, are of the highest order,” Silversea told ABC.

One CDC inspector poured concentrated chlorine over the trays once they were discovered, to prevent the food from being served to guests.

Errors in the cooling process for refrigerated items at one of the ship’s restaurants and mildew on a refrigeration unit used to store fruit consumed by passengers was also discovered during the inspection.

“The unannounced inspection on June 17 occurred at the end of the breakfast period where pots, pans and utensils were on working stations and items to return to the galleys were on trolleys as were stores from the fridges ready for use,” Enzo Visone, Silversea Cruises’ CEO, said in a statement.

The CEO further explained that staff quickly tried to remove trolleys of food and items not in the refrigerator once they heard CDC officials were on board, rather than continue with breakfast service.

“It goes without saying that such practices are against company policy and should not have happened. We would also like to make clear that following the inspection of Silver Shadow, all food found in the cabins was destroyed and under no circumstances was improperly stored food served to any guests,” Visone said.

The company later released a statement saying cruise staff responsible for the failing grade had been released from the company.

Silversea Cruises says they have improved crew training and made several other changes since the first reports of unsanitary conditions on the ship. The initial inspection took place last month, but the CDC did not release their report on the incident until last week.

As part of the Vessel Sanitation Program, the CDC conducts unannounced inspections of passenger ships docking in U.S. ports twice a year and grades them on a 100 point scale. A score below 86 is considered a failing grade.

Eleven of 179 Silversea inspections have resulted in unsatisfactory grading.