DULUTH, Minn. (AP) -- The Lake Superior Zoo says it has lost several animals in the damaging flood waters.

Duluth Mayor Don Ness says he plans to declare state of emergency because of serious flooding.

Ness says the city is encouraging people to stay home, both because of the amount of standing and rushing water from heavy rains overnight, and the difficulty in spotting hidden hazards.

A zoo spokeswoman says a "beloved" donkey named Ashley died as well as sheep and goats in the zoo's barnyard area. Parts of the zoo were under water, including the train depot.

The flooding enabled the zoo's polar bear, Berlin, to escape her exhibit. Police spokesman Jim Hansen says officers helped zoo staff track down the bear overnight. It was tranquilized and returned to its cage.

Hansen says even though a big, white object might be easy to find in the dark, it was still unnerving for the officers.

The zoo says no animals escaped the perimeter fence.