Lava started to spew from an erupting volcano in southern Chile yesterday and authorities ordered the immediate evacuation of all remaining residents from a nearby town. Chaiten volcano, in Patagonia around 760 miles south of Chile?s capital Santiago, began erupting on Friday, sending a towering plume of ash into the sky that has since coated the surrounding area and has reached as far as Argentina.

The National Emergency Office said the volcano was spitting bits of lava and rock, and that around 300 remaining civilians and troops were being evacuated by boat across a fjord. However, emergency officials had not yet detected lava flow down the volcano?s sides. Local television reported loud groaning sounds emanating from the 3,280-foot volcano, which had been dormant for thousands of years.

?The situation has changed suddenly.Today the volcano is erupting with pyroplastic material on a different scale,? national emergency official Rodrigo Rojas said in an interview. ?We ... have ordered immediate precautionary evacuation of all civilians, military and press in Chaiten.?

Authorities have already evacuated around 4,200 people ? nearly the whole population ? from Chaiten, which is six miles (10 km) from the volcano. Evacuation is complicated by the fact southern Chile is fragmented by fjords and access is often difficult. ?We hope the evacuation happens in an optimum way,? said President Michelle Bachelet, who visited the area on Monday. ?I hope this evolves in the least harmful way possible.?

Luis Lara, a government geologist, said he did not expect a catastrophic collapse of the volcano, but that a cloud of dense, very hot material could coat the surrounding area. ?This produces a more complicated scenario. A dense cloud of pyroplastic material could move down its slopes, and that causes much more damage (than a spray of lava). The entire volcano will not (collapse), but the eruptive column could, and that is sufficient material to be displaced down its sides and into areas nearby. Lava flow would not reach Chaiten, but hot fragments, ash and gas could.?

Authorities are also evacuating a second town, Futaleufu, coated with ash. Some of its 1,000 or so residents had already crossed into neighbouring Argentina, where some areas have also been showered with ash and where authorities last week closed schools and treated some for breathing problems.

The ash is more than 6 inches thick in places, contaminating water supplies and coating houses, vehicles and trees and authorities are moving thousands of cattle. Chile has the world?s second most active string of volcanoes behind Indonesia.