Darmin Nandu was confirmed dead at 2.55am, believed caused by saxotoxin, a main component of Red Tide.
Another 17 were hospitalised, bringing the number of suspected cases reported since January 13 to 43 so far.
Two others, a boy aged 14 and another aged 9, also died after consuming shellfish from Sepangar waters on Jan. 2 and 4.
Deputy Health Minister Datuk Rosnah Haji Abdul Rashid Shirlin said the Fisheries Department is currently analysing shellfish samples from the Inanam Night Market.
According to Rosnah 37 of the cases were reported here and six in Tuaran.
The Red Tide warning was first issued by the Fisheries Department on Dec 12 last year.
In the most serious case of paralystic shellfish poisoning (PSP) this season, Sabah Fisheries Department director Rayner Stuel Galid said the victims had all purchased cockles and bivalves from street peddlers at the Inanam market.
He said the red tide warning was still in place and urged the public to avoid consuming all types of marine shellfish or bivalves.
These include sea oysters, mussels, cockles, bivalves and any type of clam-like seafood.
Beginning late November, the department detected a high amount of PSP toxins in samples of bivalves obtained from the west coast through its red tide monitoring programme.
Among the initial symptoms include tingling lips and tongue, a sensation of the 'pins and needles' on the skin, followed by loss of control of arms and legs, and difficulty breathing that could result in death.