Authorities say a flow of raw sewage from Mexico across the Arizona border into Naco has been slowed, but there's still some pooling on private property in the area.
County officials say there's no immediate threat to the public and work is ongoing to contain and chlorinate the pooled sewage.
They say a pipeline leak occurred early Sunday near the Naco Point of Entry and its cause isn't immediately clear.
Area residents were told to prepare to leave their homes if the flow couldn't be stopped within 24 hours, but the pre-evacuation order was later canceled.
Crews from the county environmental health department, Arizona Department of Environmental Quality and Naco Fire Department responded to the scene.
The Naco Water Company increased its testing and treatment of the water supply Sunday.