JAKARTA (Deutsche Presse-Agentur) -- Indonesian health officials were working Tuesday to prevent outbreaks of disease as thousands of villagers remained in evacuation centres after the eruption of a volcano on Sumatra island, officials said.

Close to 29,000 evacuees were crowded into centres in Indonesia's North Sumatra, after the province's Sinabung volcano erupted twice at the weekend for the first time in four centuries.

Health Ministry officials said thousands of additional face masks were being distributed, and the centres were taking extra disinfection measures.

The also stepped up distribution of clean water and medicine.

"We must be aware of the emergence of infectious diseases, and for early prevention we urge the refugees to keep the environment clean," said Mujiarto, of the ministry's crisis centre.

"In addition, among other steps we are conducting disinfectant sprays at the evacuation areas," he said.

Other officials said that children and babies would get "special attention" as they were particularly vulnerable.

According to the National Disaster Management Agency the number of evacuees reached 28,756 on Tuesday, crowded into around 20 temporary shelters set up in government buildings or meeting halls.

Muhammad Irsal, field coordinator for the Indonesian Red Cross, said that up to 2,500 of the evacuees had developed health problems, mostly respiratory issues, eye irritation or diarrhoea.

The problems were triggered by the cold weather, volcanic dust and ash and poor sanitation, he said.

"From the survey team, the refugees need more blankets, jackets, food and masks, as well as medicines for acute respiratory infection," Irsal said.

Dormant for 400 years, the 2,451-metre-high Sinabung volcano, located in Karo district, erupted early Sunday, prompting the evacuation of thousands of residents from its slopes.

A more powerful eruption followed on Monday, forcing thousands more villagers to flee.

As many as 31 villages are located inside the official danger area, with 12 hamlets within 6 kilometres of the crater classified as the most dangerous place, requiring the area to be evacuated.

Indonesia has the highest density of volcanoes in the world with about 500 the 5,000-kilometre-long archipelago nation. Nearly 130 are active and 69 are listed as dangerous.

Copyright 2010 dpa Deutsche Presse-Agentur GmbH