Police were canvassing the neighborhood in the city of Pueblo to interview people who may have seen the three girls drown Monday afternoon.
Foul play was not suspected in the deaths of 3-year-old Azucena Gandarilla; her sister, 6-year-old Amaya Gandarilla; and their 17-year-old baby sitter, Joo Lee.
A 911 caller reported the drownings, and emergency responders could not revive the girls.
Neighbor Ruth Wright said she didn't know the girls by name but that children packed the pool during the summertime. Wright says neighbors are shocked by the drownings. The pool reached a depth of about 8 feet.