Felicia Fonseca, Associated Press
In this July 6, 2009 file photo, invasive quagga mussels cover this formerly sunken boat at Lake Mead National Recreation Area in Lake Mead National Recreation Area, Nev.

PAGE, Ariz. — The discovery of quagga mussels in Lake Powell has prompted Arizona to start requiring boaters leaving the Colorado River lake to drain, decontaminate and dry their boats and watercraft before leaving the vicinity.

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The state's order is intended to help prevent the spread of mussels.

The order took effect Monday, expanding the reach of requirements already in place for Lakes Mohave, Havasu and Mead on the Colorado River and Lake Pleasant near Phoenix.

Quagga mussels can ruin boat motors and clog water intakes, such as pipes and screens on power and water-treatment plants.

The Arizona order says boats that have been in quagga-infested waters for more than five days must, upon leaving the water, be kept completely dry for seven to 18 days before their next use.