One person had also presented to Whakatane Hospital but didn't need medical attention, he said.
In Tauranga, eight people had presented to Tauranga Hospital, five were admitted and two were in a serious but stable condition.
"There are two that are being monitored closely.''
Dr de Wet believed those from Rotorua were from one family group.
He said the poisoning highlighted the importance of following health warnings.
"Although unfortunate, it's a good reminder that this can be a very serious illness,'' Dr de Wet said.
A health warning is in place from Tairua on the Coromandel Peninsula, south to Waihi Beach and along the Bay of Plenty coast to Whakatane. This includes Tauranga Harbour, Maketu and Waihi estuaries, Matakana and Motiti islands, and all other inshore islands along the coastline.
The health warning applies to all bivalve shellfish, including mussels, pipi, tuatua, cockles, oysters, scallops as well as cat's-eyes and kina (sea urchin).
Shellfish in the affected area shouldn't be eaten. Paua, crayfish and crabs can still be taken but the gut should be removed before cooking.
Toxin symptoms ranged from tingling round the mouth and face, tingling of the skin, mild weakness, diarrhoea and vomiting. In severe cases, people can suffer paralysis and respiratory failure. Symptoms usually occur within hours of a person consuming affected shellfish. Anyone suffering illness after eating shellfish should seek medical attention.
For information on health warnings in Bay of Plenty visit www.ttophs.govt.nz and click on health warnings.