One woman has died and several people are said to be unwell after what a family member said was an 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. P&O said there had not been a gastro outbreak on the ship.

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.

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.

“I keep getting these bunches of flowers at home and I just want to scream because I’m like, ‘Oh, these flowers are beautiful and mum would love them’, but she’s not here,” Ms D’Souza said.

“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 will remain on the ship until it arrives back in Sydney on Friday, where it will dock briefly before leaving again with fresh passengers.

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

“An elderly passenger sadly passed away on Saturday on Pacific Jewel and our thoughts are with her family,” the spokesperson said. “There is no reported gastro outbreak onboard the ship.”

Queensland Health said it had not been informed of gastro on a cruise ship. 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?”

Mrs Carlson lived on her own in a house in Terrigal on the NSW central coast, where she had lived for 18 years. She had osteoporosis, but remained mobile by using a walking frame, and on her last check-up appeared to be in good health.

Queensland Police confirmed a 79-year-old woman died on a cruise ship that was docked at Cairns on Saturday. Officers will prepare a report for the Coroner.