Marine researchers are looking into a mysterious skin illness that is plaguing whitetip reef sharks in Malaysia, with early findings pointing to increased sea temperatures as a possible cause.

Whitetip reef sharks, so named because of the white tips on their fins, are commonly seen resting in schools near reefs during the day and are a popular diving attraction. At night, they come out to hunt for little fish and other creatures.

After an underwater photographer captured images of one of the sharks with what seemed to be blotches and lesions on its head off the coast of Sabah state on Borneo island in April, the images went viral on social media.

Soon after, divers from neighboring Sipadan Island, as well as a team of experts from the state's university, government, and conservation organisations, began noticing the skin illness in every group of sharks they saw.

In an effort to figure out what was causing the illness, the researchers discovered that the sea surface temperature in Sipadan had risen to 29.5 degrees Celsius in May, a degree higher than it had been in 1985.

"We can almost certainly pin the warming ocean as having a role in what we are seeing with the sickly sharks in Sipadan,"said Mr Davies Austin Spiji, a senior marine biologist with non-profit conservation group Reef Guardian, ruling out human factors as Sipadan is a marine protected area where fishing is strictly prohibited, and there are no settlements or industries nearby.