All of the guests at the hotel in the Fatih district were forced to move to other accommodations, local media reports.
The three deceased, a mother and her two children, fell ill on Wednesday after eating several different types of street food from the Ortakoy area, located by the Bosphorus Bridge.
All were taken to hospital, but their lives could not be saved. The children, aged six and three, died on Thursday and the mother a day later. The father's condition is "critical," Istanbul's regional health director wrote in a post on X.
Two more tourists staying at the same hotel were taken to hospital on Saturday after vomiting.
Media outlets have tried to map out what food those who fell ill may have eaten.
But the police have also been able to establish that a room on the hotel's ground floor was recently sprayed with pesticides, which led to the arrest of a hotel employee and two pest control workers.
