Nearly 30 dead sharks found on Sea Isle City beach. An expert says this may have been how they washed ashore.

Nearly 30 small sharks found dead along a stretch of beach in Sea Isle City, New Jersey, are raising questions about what caused the animals to wash ashore.

Michelle Greenling said she counted 29 sharks during a Wednesday morning walk along the beach between 29th and 39th streets.

"The first couple weren't too surprising, but when I saw three and four and five, I knew something was up," Greenling said.

The sharks were roughly a foot long and appeared to be juvenile dogfish, according to Stephen Nagiewicz, an adjunct professor of marine science at Stockton University. Dogfish are known to travel in large schools.

Greenling said some of the sharks had red markings on their undersides, prompting concerns about what the deaths could mean for the water.

"It was definitely concerning. I was concerned about the water. I was concerned about the sharks," she said.

Nagiewicz said a toxic substance in the water is unlikely to be the cause.

"If it were some kind of toxic substance in the water, more fish would show up on the beach than just the dogfish," he said.

Instead, Nagiewicz said the sharks may have become trapped by changing tides and subsequently stranded themselves. Another possibility is that fishermen targeting other species accidentally caught the young sharks and discarded them offshore.

"It's either they got stuck in the tides and beached themselves, or somebody dumped their catch offshore and came this way," Nagiewicz said.

While finding nearly 30 sharks on the beach is unusual, Nagiewicz said it does not necessarily indicate a larger environmental problem.

Still, some beachgoers said they want officials to determine what happened.

"That's why they should figure it out," Patricia Steidel of Bergen County said. "They should try and track down what happened. And if there is illegal fishing, try and patrol it better."

The sharks were already gone by the time a CBS News Philadelphia crew arrived at the beach around noon. Nagiewicz said they were likely washed back out to sea by the incoming tide.

Beach patrol officials and the New Jersey Department of Environmental Protection were contacted about the reported shark deaths. Neither immediately confirmed the animals had washed ashore, though a DEP spokesperson said such occurrences are not uncommon.