NEW : `` The families can return to normal life , '' Toledo mayor says of water ban . By Associated Press and Reuters TV in Mexico City MEXICO CITY -- Microcystin , a toxin caused by algae blooms , found in the water system .
NEW : `` The families can return to normal life , '' Toledo mayor says of water ban . Tests showed high levels of toxins in two Toledo neighborhoods . Microcystin , a toxin caused by algae blooms , found in the water system .