Officials say one person still unaccounted for as forecast heavy rain and thunderstorms threaten further flooding

A second death was confirmed by National Park Service officials on Monday after a flash flood sent a surge of water and debris through an area of the Grand Canyon over the weekend.

Dozens of visitors had to be evacuated by helicopter during the deluge, which consumed trails and infrastructure. Nearly 80 people were rescued and one person is still unaccounted for, as more heavy rain and thunderstorms in the forecasts threaten additional debris flows, flash floods or rock falls, the NPS said in a statement.