SYDNEY, Australia - Up to three sharks may have been involved in the fatal attack on a 21-year-old woman off an island in eastern Australia, police said Sunday.

The woman, whose identity was not immediately released, died late Saturday after being attacked near North Stradbroke Island, east of the Queensland state capital Brisbane.

Queensland state police inspector Peter Harding said officers were searching for the sharks and had closed several nearby beaches.

"If we found them (the sharks) I suppose we would try to retrieve them and see if they have any body parts," Harding said. "The idea is to retrieve what we can."

The woman was swimming with a friends from a church group in shallow water about 50 feet offshore when the shark attacked, local media reports said. The woman's dog was also in the water.

The woman was airlifted to a Brisbane hospital where she had to have both arms amputated just below the elbow, according to Queensland Rescue Helicopter spokeswoman Helen Anderson. She also suffered deep wounds to her legs and torso, Anderson said.

Harding said the severity of the woman's injuries indicated she may have been attacked by a group of bull sharks, a species known for aggressive behavior this time of year.

"She was bleeding quite heavily ... (from) what I've seen and what I've been told, there was more than one shark involved, there could have been up to three," Harding said