Georgina Mitchell of The Sydney Morning Herald reports one woman has died and several people are believed to be unwell after a suspected outbreak of gastroenteritis on a cruise ship off the coast of Queensland.

The P&O Pacific Jewel cruise ship left from Sydney on September 6 for a 10-night “Barrier Reef Discovery” cruise.

Margaret Carlson boarded with her daughter and teenage grandson. It was the 79-year-old’s seventh cruise in 10 years after her husband passed away, and she was looking forward to the journey after being upgraded to a luxury cabin.

She soon began showing signs of gastro and was told by medical staff that she had probably brought the bug onto the ship with her, her family says. Her daughter and grandson also fell ill after boarding the ship. P&O denied there had been a gastro outbreak on the ship.

On Saturday afternoon, when the ship was docked at Yorkeys Knob in Cairns, Mrs Carlson’s family discovered she had died in her room.

Police were called to inspect the scene and determined she had died of natural causes several hours earlier. An autopsy will be performed.

Mrs Carlson’s daughter Vanessa D’Souza, 41, said her mother’s death was sudden and extremely upsetting.

“My first priority was to let people know, because I thought you would not want to send your mother or grandmother on that [ship].”

Ms D’Souza has been in contact with her sister, who said large numbers of cruise passengers were locked out of their rooms on Monday morning and not told why. The family believes dozens of rooms on two decks of the ship were being cleaned and disinfected.

A P&O spokesperson acknowledged the death but denied there was a gastro outbreak.

Gastroenteritis is not a “notifiable” condition, meaning there is no obligation to report such an outbreak.

One passenger was medically evacuated from the ship by helicopter on Monday for reasons which could not be divulged.

Ms D’Souza said most of the passengers on board “can’t wait to get off”.

“We’d like some answers,” she said. “Is there really some issue with hygiene, or is there something going wrong?”