NEWPORT, Ore. - A number of young sharks are washing up dead on Oregon's beaches this summer, but researchers are unsure why.

The dead sharks reports started in mid-August, said Bill Hanshumaker, public marine education specialist at the Hatfield Marine Science Center.

"I've had more reports this summer than I've had since 1993," Hanshumaker told The Oregonian.

One theory is that warmer water this summer lured tuna and other bait fish closer to shore, and the sharks followed. When the sharks die farther offshore, their remains are usually consumed. But when they die close in, they are more likely to wash up.

There have been reports from California of dead sharks testing positive for encephalitis, which can be caused by viral, bacterial or protozoan infections, said Jim Burke, director of animal husbandry at the Oregon Coast Aquarium.

Two salmon shark carcasses washed ashore this week, said Keith Chandler, general manager of the Seaside Aquarium, bringing the count there up to seven. Two soupfin sharks also were found in the area.

The sharks are usually reported as baby great whites but almost always turn out to be young salmon sharks, which have a similar body form but not serrated teeth.

In addition, a decomposed whale believed to be a humpback that had been dead for weeks washed up on Del Rey Beach north of Gearhart this week.

"It's much too early to speculate," Burke said. "Salmon sharks give live birth right along the coastal area so we often see newborn to juvenile sharks wash up. This year there definitely have been quite a few more than usual. It's hard to tell if there have been more born or if there is something gone wrong. "

At this point, marine experts say they're not concerned but curious, and watchful for anything that might suggest something out of ordinary.