Hazardous material teams recorded "extremely hazardous" levels of hydrogen sulphide in a toilet cubicle of a luxury cruise vessel in the hours after a woman's body was found on Saturday afternoon.

The woman, who can now be identified as Shalina Abdul Hussien, was found slumped in a confined toilet cubicle on the Lady Rose, a three-level vessel owned by cruising company All Occasion Cruises Pty Limited.

The Lady Rose cruise ship, on which a 39-year-old woman was found dead. Credit:Instagram

It is now understood that while earlier readings conducted by Fire and Rescue teams on Saturday afternoon were "not alarming" and reflected a "safe atmosphere," by 8.30pm on Saturday further testing by HAZMAT teams recorded "extremely hazardous" levels of hydrogen sulphide, that reached the highest possible levels that could be recorded by testing machines.

Despite these findings, a spokesman for Fire and Rescue NSW disputed them, saying that the levels were "not consistent with what we found on Saturday," adding that the readings taken at the time of the incident were of such a safe atmosphere that crews did not even return to the vessel for further testing on Sunday.