Mount Sinabung on the Indonesian island of Sumatra on Monday erupted for a second time, forcing more than 20,000 people to remain in evacuation centres, officials said.

The Volcanology and Geological Disaster Mitigation Centre said Sinabung’s second eruption occurred at 6:30 am (2330 GMT Sunday), belching a column of smoke up to 2,000 metres into the sky.

The 2,451-metre-high volcano erupted for the first time in more than four centuries early Sunday, prompting the evacuation of thousands of residents from its slopes.

Sunday’s eruption came only hours after the local government allowed residents to return to their homes, assuring them that the volcano was not dangerous.

The Sinabung volcano, located about 1,300 kilometres north-west of Jakarta, has been seen heating up since late Thursday, causing people living on the slopes to flee.

The number of refugees had reached 21,054 people by Sunday morning, said Jhonson Tarigan, a Karo district public relations official.

“The number is likely to increase if the situation gets worse,” Jhonson said.

Vulcanologists upgraded Sinabung’s danger status to the top level minutes before Sunday’s eruption, and revised its status from a dormant to an active volcano.

“Previously, there was no significant activity at the Mount Sinabung volcano, so the monitoring did not take priority since the 1600s,” Surono, the head of the directorate who like many Indonesians uses only one name, said on Sunday.

He recommended the residents remain at the evacuation centres until further notice.

Besides ordering the evacuations, experts also warned residents to wear face masks against the volcano’s ash and told people living along rivers to watch out for possible lava-induced floods.

Indonesia has the highest density of volcanoes in the world with about 500 in the “Belt of Fire” in the 5,000-kilometre-long archipelago nation. Nearly 130 are active and 68 are listed as dangerous.

More In: International | News