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John Locher, Associated Press
Melanie Vallet, left, and Madison Bush rescue a mule caught in floodwater Tuesday, Sept. 9, 2014, in Overton, Nev. The flood water came from heavy rain Monday that also washed out parts of Interstate 15.

MOAPA, Nev. — Nevada Gov. Brian Sandoval has dispatched a team to start estimating the cost of damage from flooding that wiped out swaths of a vital interstate and swamped parts of Clark County and a southern Nevada Indian reservation.

Sandoval also declared a state of emergency late Tuesday to allow local governments to qualify for state and federal help after Monday's storm.

Monsoonal moisture combined with remnants of Tropical Storm Norbert to dump water throughout the Southwest earlier this week. The small town of Moapa received more than 4 inches of rain in two hours.

Clark County officials said damage included at least 30 flooded homes in nearby Overton and crumbled pavement on a nearly 50-mile portion of Interstate 15 that could be closed for days.