Unconfirmed sources said another person died in the evening, though his identity could not be established. Nearly 40 people have been taken ill, sources said, and are all admitted in the Paharpur nursing home nearby. Most of them are children, six of them serious.

Sayesta’s mother Niga Multana said the child had been ill since Sunday night. Though she was being treated, her condition took a turn for the worse on Monday morning. She died on her second visit to the doctor.

The disease has struck in the Bangali Bazar area of Garden Reach. People came down with it last Friday, with locals accusing the Kolkata Municipal Corporation (KMC) of supplying contaminated water. They said the water has been dirty for the last six months.

A civic official said the water turned bad because of the ongoing restoration work the KMC has undertaken to spruce up its pipelines. The work is being operated by the KMC’s nodal arm, the Kolkata Environment Improvement Project. Officials suspect drinking water has been mixed with sewage during the work.

Member Mayor in Council, Health, Subodh Dey said: “As soon as we got news, we sent two health teams to the spot. We will also be supplying drinking water to the area till the water contamination is dealt with.” Two health camps have been set up at Moulana Azad School and Tikiapara, officials said.

Local Inam Alam said: “There has been a problem with drinking water for the last six months. We approached officials several times but no one came to our help. The water we get stinks and often has insects floating in it.” Local residents also said they have been asked to boil the water before drinking. However, since many of them are daily wage earners, this is an expensive proposition. Alam said: “We earn as little as Rs 50 some days. Kerosene is expensive. How can we boil water all the time?”

Badruddoza Molla, the chairman of the borough, said: “This outbreak could be caused by the bad weather. Our health officials are visiting the spot. We are meeting the councillor to monitor the situation. We are also aware that a child is dead.” He said the two medical camps have four doctors in each, as well as 10 health officials. Molla however denied 40 people had been affected, pegging the number between 20 and 25.

Trinamool Congress chief Mamata Banerjee was also at the spot in the evening after locals blocked the arterial road in the area for nearly one and a half hours since 3 pm.