MORONI, Jan 16 (Reuters) - Authorities in the Comoros islands have made emergency plans to help as many as 30,000 people expected to be uprooted if one of the world's largest active volcanoes erupts, officials said on Tuesday.
The 2,361 metre (7,746 ft) high Mount Karthala on the Indian Ocean archipelago's biggest island, Grande Comore, began glowing red and emitting fumes on Friday.
Strong tremors over the weekend -- thought to have been caused by lava trying to escape -- forced thousands of people to sleep outside for fear their homes might collapse.
The island's security chief, Oukacha Jaffar, told Reuters as many as 30,000 people could be displaced by an eruption.
"We have planned for the creation of two advance medical posts in the central and western zones, while primary and secondary schools will be used for first aid," said Hamada Goda, a doctor at one of the medical posts.
Hamidou Soule, a geologist who leads the Karthala surveillance centre, said satellite images clearly showed a build-up of heat on the northern edge of the crater.
"There are three possible scenarios: a crack on the side of the mountain mass, an overflow from the crater, or simply a settling of activity," Soule told journalists.
Karthala's eruptions have happened every 11 years on average, but have rarely caused a major disaster.
In 1903, 17 people died when noxious fumes seeped from cracks in the mountain, and the last big eruption was in April 2005 when thousands fled in fear of poisonous gas and lava.