The body of a 70-year-old German woman washed up on the shore at Egypt's Sharm el-Sheikh on the Red Sea after an attack Sunday. Officials said the shark had taken a chunk out of her right thigh and bitten through her right elbow.
Egypt had just lifted a ban on swimming in parts of the area imposed after three Russians and a Ukrainian were injured in shark attacks last week.
The government has invited international experts to help locate the killer shark but officials were at loss as to what could have caused its behaviour.
"There is not one reason that will be ignored. We are seeking any reason that causes a change in shark behaviour," Ahmed el-Edkawi, assistant secretary for the South Sinai region, told Reuters.
Some said sharks had been drawn to shallow waters after cattle being shipped in for last month's Islamic feast of the sacrifice, or Eid al-Adha, had died and were thrown overboard.
Others suggested it could have been part of a secret plot by Israel's Mossad intelligence agency.
"What is being said about the Mossad throwing the deadly shark (in the sea) to hit tourism in Egypt is not out of the question, but it needs time to confirm," South Sinai Governor Mohamed Abdel Fadil Shousha was quoted as saying by state news site egynews.net.
Egyptians often blame neighbouring Israel for a variety of problems such as drug and weapon smuggling, or say it supports media that seek to portray Egypt in a bad light.
Local diving experts said single shark attacks are extremely rare in the area and were mystified by as to why so many people were attacked in such quick succession.
The attacks grabbed the attention of world media and raised fears of a long-term hit to a tourism sector that is a lifeline for the desert peninsula's population and the biggest foreign currency earner for Egypt.
"We've seen more attacks in a few days than in the previous 15 years," said Florian Herzberg, dive operations manager at the Reef 2000 centre in Dahab resort north of Sharm. "It could be a shark with behavioural problems that was deliberately fed different things and now associates humans with food."
Water sports centres said business had dried up after officials banned snorkelling and swimming, leaving tourists with little to do but speculate over the cause of the attacks.
"Egypt is full of rumours and one does not know what to believe," said Gasser Mohamed, a diving instructor at CFun Divers centre in South Sinai. "I see that there are a lot of sharks in the sea and the possible rarity of tuna fish due to over-fishing seems to be causing the attacks."