Wildlife experts have found hundreds of deadly box jellyfish beached in northern Australia. The mass death has them baffled. More than 500 were found dead or dying on a beach near the northern city of Darwin last weekend. "It's something that you don't see anywhere else, and we have never seen it before," said Jamie Seymour, a jellyfish expert at James Cook University.

Box jellyfish, also known as chironex fleckeri, infest waters across northern Australia between October and April. They have been blamed for killing more than 60 swimmers in the country over the years.

Seymour expressed concern over the jellyfish deaths. "Jellyfish are often used as a measure of the health of the environment," he said.