SACRAMENTO, Calif. (AP) — Rain in the forecast starting Wednesday could aid crews fighting California's deadly wildfires while raising the risk of flash floods and complicating efforts to recover remains of those killed.

Residents in communities charred by the Los Angeles-area fire stacked sandbags as they prepared for possible downpours that threatened to unleash runoff from hillsides left barren by flames.

In Northern California, teams continued sifting through ash and debris as they searched for bodies in and around the decimated town of Paradise.

"The task is arduous," said Rick Crawford with the California Department of Forestry and Fire Protection. "And the possibility exists that some people may never be found."

With the death toll at 81 in the state's most destructive wildfire, there are still nearly 870 people still unaccounted for.

Authorities trying to identify the scores of people killed are using rapid DNA testing that produces results in just two hours. The system can analyze DNA from bone fragments or other remains, then match it to genetic material provided by relatives of the missing. But the technology depends on people coming forward to give a DNA sample via a cheek swab, and so far, there are not nearly as many volunteers as authorities had hoped for.