A senior Solomon Islands health official fears contaminated water sources in the capital might have gone undetected if random checks hadn't been conducted by the council.
The health director for the Honiara city council, Dr Henry Kako, says it may have caused chronic diarrhoea among children.
He says when the council found out last month that of 22 water samples in Honiara, 20 contained bacterial and fecal contamination, public warnings were promptly issued.
"In the Congulai source, we found that there were total coliforms that we've detected, including e-coli. Also that's the same results for the Rove source, while for Tuvuruhu and the Henderson bore hole we've detected just total coliforms, not e-coli."
Dr Kako says until further notice, affected residents are being urged to boil water, use bottled water or rainwater from tanks.
He says fixing the problem is the sole responsibility of the Solomon Islands Water Authority.