ALBUQUERQUE, N.M. (AP) - After a solid month of battling flames, crews have nearly contained the largest fire in New Mexico's history.

But as summer rains pound the burn scar of the Las Conchas fire, ash and debris are being washed off mountainsides, down canyons and into the Rio Grande.

That has forced utilities in Santa Fe and Albuquerque to halt their drinking water diversions until the river clears up.

Debris is making its way to Cochiti Lake south of the burn area, and a layer of black ash has been spotted on some sand bars in the river between Cochiti and Albuquerque.

Environment Department Deputy Secretary Raj Solomon says his agency is sending out teams to take samples from the Rio Grande. He says the focus is on sources of drinking water supplies.

(Copyright 2011 by The Associated Press. All Rights Reserved.)