The town has reported over 553 cases of the bacterial infection during last five days.
"Gastro has claimed three lives so far," said District Collector Deependra Singh Kushwah.
However, unofficial estimates put the figure at 13 though it cannot be verified.
Out of 553 patients diagnosed with gastro so far, 377 patients have been discharged after treatment.
"The levels of infectious bacteria are high in water. The water from the drainage pipelines is seeping into pipelines carrying water causing the contamination," said municipal corporation commissioner Ajij Karche.