The raspy cries of oil-soaked sea otters join the soft wheezing of sick harlequin ducks inside the ugly orange building in the center of town.

The nation's biggest oil spill was in its 11th day Monday, and the number of oil-soaked otters and birds being picked up from the once-pristine waters of Prince William Sound was rising.Biologists and volunteers, wearing yellow rubber coveralls and boots, worked grimly washing otters and birds brought in by boat and aircraft. A refrigerated truck trailer served as a morgue for those that didn't make it.

By late Sunday, the Bird and Animal Rescue Center had washed and treated about 150 birds and 28 otters, 11 of which later died, said a spokesman for the hastily constructed center, which is financed by Exxon.

"It's absolutely wrenching in some of those heavily oiled areas," said John Lyman, a spokesman for the Alaska Department of Fish and Game.

He said he set a videocassette down on a black rock as he filmed one area, and the rock began crawling. It turned out to be a seabird covered with asphalt-hard oil.

"You can't see these oiled otters and birds from the air," said Bruce Baker, another state wildlife official. "You walk along and there they are, a black bald eagle, a seabird."

Randy Davis, a spokesman for Sea World of San Diego, which is operating the center with the International Bird Rescue Center of Berkeley, Calif., said seals, sea lions and whales apparently have not been affected, although they probably will be. Sea otters lose their buoyancy and warmth from the oil and freeze to death or drown, he said.

Even rescued otters are hard to keep alive. "We're looking at a 60 percent recovery," Davis said. He expects the center to have treated dozens of dark-eyed otters before long, and scores will be sent south for rehabilitation, he said.