The three upazilas are Chuadanga Sadar, Almadanga and Damurhuda. Survey is going on in Jibannagar upazila, officials at the district Public Health and Engineering Department (DPHE) said.

Of the patients, 86 are in Chnadanga Sadar, 555 in Alamdanga and 224 in Damurhuda upazilas.

Of the 77,500 tube wells tested out of total 80,548 in the district, water of 27,317 have been found arsenic- contaminated.

The arsenic-affected tube wells are 3,123 in Sadar, 15,225 in Alamdanga and 7,469 in Damurhuda upazilas.

DPHE has sealed all these tube wells and is implementing a massive programme to face the situation. These include digging of 'ring wells', preservation of rainwater and motivating people, the officials said.