For the third week in a row, no traces of dieldrin have been detected in a Yigo water well that was contaminated with the pesticide.
If results from a fourth week of testing come back clean, Guam Environmental Protection Agency will lift the advisory warning people not to drink the water without treatment.
After more than 1,100 Guam Waterworks Authority customers in Yigo were told their water was contaminated with a chemical used to kill termites, the agency installed an interim treatment system at well Y-15.
The system, which was completed Oct. 10, uses activated carbon filtration to remove contaminants.
A permanent treatment system is in the works, and should by completed by next summer, officials said.