The father, Servet, 38, died yesterday. The exact cause of their deaths remains unclear.
Last Tuesday, the family had visited the Besiktas district of the city where they tried the street snack midye – stuffed mussels.
They later went to a local restaurant where they ate dishes including kokorec, made from calf intestines, and tavuk tantuni, a type of Turkish chicken wrap, according to reports.
Istanbul’s Chief Public Prosecutor’s Office has launched a major probe, and a total of 11 people have been detained, including street vendors.
Investigators are examining whether the mussels or food at the restaurant was the trigger, or whether chemicals used by a pest control service at the hotel led to their deaths.
Evidence later emerged that the family may have been exposed to pesticides in the hotel where they were staying, Turkish media reported.
Turkey’s Hurriyet newspaper said a substance was sprayed in a room on the ground floor of the hotel to combat a bed bug infestation, which may have reached the family’s room on the first floor through a bathroom vent.
Samples from the food stalls and restaurants are also being analysed by Istanbul’s Forensic Medicine Institute.
Among those detained were five food sellers, the hotel’s owner and two staff, and three people from the pest control company.
According to a local newspaper, two other tourists staying at the same hotel were also hospitalised on Saturday with similar symptoms.
Turkish President Recep Tayyip Erdogan, 71, said “The investigation is currently being carried out comprehensively. It will be revealed what caused the deaths .”
Back in August, two Italian people died and over a dozen were hospitalised after eating a broccoli and sausage sandwich from a food truck near the town of Diamante in Calabria, Italy.
They were all displaying signs of botulism poisoning.