HONOLULU (AP) — Initial observations indicate a surfer was bit by an eel, not a shark, over the weekend off Hawaii's popular Waikiki Beach, but officials said they're working to confirm that.

The surfer was hurt Saturday, hours after a shark attacked a man off Oahu's Lanikai Beach. The men were hospitalized in serious condition. Updates on their injuries weren't immediately available Monday.

The state Department of Land and Natural Resources was waiting to interview the man hurt off Waikiki to make a final determination about which sharp-toothed creature bit him, agency spokesman Dan Dennison said.

Hawaii's coral reefs are home to a variety of eels, including some with large mouths and sharp, long teeth that help in capturing prey. They usually are not dangerous or aggressive unless provoked, the Maui Ocean Center's website says.

Dennison said this is the first time he had heard of a possible eel attack in Hawaii waters. The state does not keep records of such bites, as they do for sharks, he said.

In the earlier attack, witnesses said a tiger shark bit a 44-year-old man off Lanikai Beach around noon Saturday.

The man was swimming to shore from the Mokulua Islands, Honolulu Emergency Services spokeswoman Shayne Enright said.

He was attacked about 50 to 100 yards from shore, according to the Honolulu Fire Department. A local man helped him to shore on an outrigger canoe, she said.

Saturday's bite was the sixth confirmed shark encounter in Hawaii this year, and the second in as many weeks on Oahu, state statistics show. A man lost his leg when a tiger shark bit him on Oahu's North Shore less than two weeks ago.

Most shark bites this year have happened in turbid or murky water, and all so far have resulted in injuries. In April, a shark killed a woman while she was snorkeling off Maui.

Fourteen shark encounters occurred in Hawaii in 2013, and two were fatal. Two did not involve injuries as the sharks bit surfboards but not the people riding them.

In 2014, there were six shark encounters, but three involved no injuries. None of those attacks were fatal.

Officials recorded an average of 4.2 shark encounters per year from 2005 to 2009. Since 2010, the average has increased to 8.6 per year.

Dr. Carl Meyer, a shark and reef researcher at the University of Hawaii's Institute of Marine Biology, said Hawaiian oral traditions and current statistics show shark bites are more common in the fall.

"Hawaiians have also long known that fall is pupping season for tiger sharks, and the 'fall spike' in shark bites may well be linked to this natural, annual phenomenon," Meyer said in a statement Monday.

However, he noted shark bites happen in the state year-round, and the number of bites is very low compared with the number of people in the ocean.

"The number of people living in Hawaii and using the ocean for recreation has increased over time, and this is the single most likely reason for a higher number of shark bites in recent years," Meyer said.

Officials warn people to stay out of murky water because of an increased likelihood of shark bites. Sharks are able to see well in conditions that humans cannot, making dark, murky water especially dangerous to swim in. The water was turbid Saturday after several days of rain and stormy weather.

Hawaii Tourism Authority president George Szigeti said in a statement Monday that the weekend's bites were isolated but that people should be aware of the dangers in the ocean.

"As an island state, we are surrounded by the ocean, so it is important that both our visitors and residents take precaution to understand ocean safety and take precaution when entering the water," he said.

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