Fishermen in the waters between Java and Sumatra were warned to remain far from the rumbling volcanic island, which was spewing columns of ash and globs of lava.
The greatest threat to people living in the South Lampung region would come from a tsunami should the volcano explode violently.
An 1883 eruption of Krakatoa produced a tsunami that killed about 40,000 people, and spewed enough ash to change the world’s weather for several years.
That explosion is still considered to be the loudest sound ever heard in modern time, with reports of it being heard nearly 3,000 miles away.
Scientists said their monitoring equipment on the slopes of Anak Krakatau stop working periodically after ash covers the solar cells powering the units.
Occasional rainfall washes off the ash, allowing the units to work for brief periods of time.
Anak Krakatau has grown by an average of 22 feet per year, with nearly daily eruptions of lava occurring since its most current eruptive episode began in 1994.