CRESTON, Iowa (AP) — People in four Iowa cities have been told they can once again safely drink water from their taps.

The Southern Iowa Rural Water Association says the treatment system is back up and running with new filtration membranes. Three cities given an all-clear Monday were Afton, Diagonal and Lenox. Creston was cleared Sunday.

The advisory remains in effect for people in rural areas around Creston and in several counties served by the association.

A membrane filtration system failure at the Twelve Mile Water Plant in Creston had left association customers without safe tap water since June 1. People were advised to boil tap water before consumption to avoid pathogens and parasites that could cause illness.

The water was considered safe for bathing and for pets and livestock.