The health officials, investigating contamination of seven wells in Taleigao today indicated that it may be due to mixture of ammonia in ground water. Though the final laboratory report on the water samples of five wells, is expected on Friday, sources in the department indicated that it may be due to mixture of ammonia. Samples of two others were not taken as they are in close proximity with the four. Last week seven wells in Chincholem and four in Borbhat, from Taleigao were reported to be contaminated with dead fish floating over the whitish colour water giving a foul smell. The officials, led by sanitary inspector Anil Killedar visited the wells and took samples of the water in the presence of some corporators and panch members, which was sent for laboratory test at health headquarters. The contamination of wells was first reported by the Herald last week. "As of now the indications are there is a mixture of ammonia in wells,' he said declining to speak any further on the reports as they in the process of testing. "We have treated all seven well after they were emptied by the authorities concerned,' Killedar told Herald today. "Only three wells were used for drinking water purpose while the rest were used for washing etc,' he said. Asked what could be the reason and whether he suspected some mischief for the contamination, Killedar replied in the negative. "I am surprised as the water now had become blackish from its earlier whitish colour and I personally do not foresee any mischief by anyone,' he said. Substantiating his claim, Killedar said "though the wells in Chincholem are in open and some one can play mischief by throwing something inside, the wells in Borbhat were in thickly populated areas and I don't think anybody would dare to do such thing.' Apart from cleaning the well, the department has also introduced some fish in the wells to avoid mosquito breeding. The sanitary inspector also suspected that the contamination could be at the ground water table and "if it is so it would be a tough job at hands for everybody.' Mr PBS Hede, Scientific officer, Directorate of Health Services, when contacted for his opinion on the issue said "At this point I am just as surprised as you are and will be able to comment only after the report is out,' he said.