ST. LOUIS (AP) — Experts say more intense storms driven by climate change are boosting contamination risks for privately-owned drinking water wells.

While estimates vary, studies say roughly 53 million U.S. residents rely on private wells that draw groundwater. Flood waters pick up bacteria and other contaminants that can seep into wells and cause illnesses.

Tests have detected elevated levels of E. coli in some wells after Hurricane Harvey and other major storms. Even ordinary rainfall can be a threat.

Private wells are largely unregulated and many owners don’t regularly test their water. Scientists say regular sampling and simple maintenance can help protect those who drink well water.

By MICHAEL PHILLIS and JOHN FLESHER, Associated Press