PRINEVILLE, Ore. (AP) _ A creek running through this Central Oregon town overflowed its banks, forcing the evacuation of 285 homes and damaging many of the structures, emergency officials said today.

No injuries were reported.

The Ochoco Creek, normally a small waterway that bisects this high desert town of 6,000 people, turned into a murky fast-moving river Friday night after an upstream dam overflowed, said T.J. Johannsen, emergency incident spokeswoman.

Oregon Gov. John Kitzhaber declared Crook County a disaster area.

She said the flood waters rose gradually, allowing the orderly evacuation of the homes. Emergency boats and helicopters were standing by, but authorities did not need to use them.

``We've been real fortunate,'' Johannsen. ``The evacuation went very well. We have a swift water evacuation team and boats and helicopters available but we haven't had to use them.''

She estimated that one-fifth of the town was under water.

The Ochoco Dam overflowed after the area, which normally gets nine to 12 inches of rain a year, got more than an inch of rain from a storm Friday.

But the dam held and was in no danger today, Johannsen said.

Carrie Sammons, another emergency spokeswoman, said earlier reports that the creek had crested proved wrong.

She said it continues to rise slowly, with a crest expected about noon.

More evacuations may be needed. she said.

Once it does crest, it is predicted to remain at a high level for at least 24 hours before it begins to drop, allowing authorities to permit residents to return to their homes.

Two shelters were opened for the evacuated residents, one at the Calvary Baptist Church and one at the Pioneer Memorial Hospital, both north of Prineville.

Sammons said about 40 people used the shelters Friday night. Many elected to go to the homes of friends and relatives instead.

Johannsen couldn't estimate how many of the evacuated homes were damaged, but she said that ``a good portion'' of the homes suffered some damage.

``We haven't been able to get in there to assess the damage, but it's extensive _ they are full of water,'' Sammons said.

Johannsen said residents reported a slow but steady increase in the water level Friday night.

``Some people told us they had four inches of water in their homes and it was up to a foot an hour later,'' she said.

Local police officers and sheriff's deputies joined with 50 National Guardsmen and volunteers to sandbag areas threatened by the flood waters, she said.

Prineville resident Steve Arnce said the water rose from street level to his garage in about two hours.

``It was at the road and then it was at the house,'' he said. ``And no, we don't have flood insurance.''

Todd Robinson said flood waters were in the crawl space of his rental home and were about a foot deep in the back yard.

``I'm moving,'' Robinson said. ``I swear to God I'm moving to Arizona.''