Scientists are keeping an eye on Whakaari/White Island after volcanic ash and strong gas has been detected in the crater..

GNS Science says onsite cameras showed a minor emission of light brown ash from an active vent behind the lake, rising to about 600 metres above the volcano on Sunday.

It says the most likely explanation is a small batch of magma moving into the shallow part of the volcano, rather than an eruption.

The Volcanic Alert Level remained at a state of moderate to heightened unrest, and the aviation industry has been warned of possible minor ash emissions.

-RNZ.