Rumblings at the other volcano forced thousands of people to evacuate.
Local vulcanologist Hendrasto described the simultaneous activity at Mount Bromo and Mount Awu as "pure coincidence". Indonesia sits astride the geologically active Pacific "ring of fire" and has more than 100 active volcanoes.
Situated on Sangihe island, 2250km northeast of Jakarta, Mount Awu showed no sign of calming and belched out more hot smoke and ash on Wednesday.
Samuel Dalompha, an official of the Directorate of Vulcanology on the island, said the column of smoke was now two kilometres high.
As many as 20,000 people on Sangihe, which is near the Philippines, have been evacuated from the mountain's slopes and immediate vicinity.
One of the most active volcanoes in the sprawling archipelago, Awu has erupted repeatedly since the 17th century. Nearly 3000 people died when it blew up in 1812.
The volcano's last fatal eruption was in 1966 when 40 people were killed. It has erupted on a number of occasions since then.
Meanwhile, thick brown smoke continued to hover above the 2392m Mount Bromo on Wednesday in densely populated East Java province.
An eruption on Tuesday killed two tourists, one an Indonesian and the other from Singapore.
Mount Semeru, next to Bromo,
began to smoke on Wednesday
At least three more people were reported missing and search and rescue officials planned to comb the slopes of the volcano, some 750km east of Jakarta.
Dozens of international tourists were still seen in the area on Wednesday despite appeals by officials to leave.
Indonesia sits astride the geologically active Pacific "ring of fire" and has more than 100 active volcanoes.
Local vulcanologist Hendrasto said the increased activity at the two volcanoes was unrelated.