Chile's government on Thursday called for a forced evacuation of communities within a 20-km radius of the Calbuco Volcano, which erupted twice Wednesday after lying dormant for more than half a century.

The volcano, situated in Chile's southern Lake District, spewed a mushroom cloud so thick and extensive that, according to one Chilean meteorologist, the ashes are likely to reach the nation's capital Santiago by Friday, despite it being more than 1,000 km away.

"We are far enough away so that the particles that do arrive will be very fine," Rene Garreaud of the University of Chile told Chilean daily El Mercurio, adding the ashes will probably float above the city and present no health risks, though they might affect flights.

Prior to traveling to the region, Chilean President Michelle Bachelet decreed a "health warning" for all the communities near the volcano.

She also said 11 shelters had been readied for the 4,150 people evacuated, and "that no deaths have been reported."

A hiker initially reported missing turned up Thursday with minor injuries. Waldo Flores, 21, said he lost his way on the mountain Wednesday before the eruptions and was forced to spend the night in the woods.

The ash cloud led to the closing of five border crossings with neighboring Argentina, whose Andean resort town of Bariloche reported falling ash.

Chile's national geologic service (Sernageomin) said the situation could be aggravated over the coming hours, following the emission of lava and incandescent rocks during the second eruption.

"We don't know how this is going to evolve," Bachelet said. "It's quite unpredictable, it could die down, it could erupt again or, like the Chaiten Volcano, it could maintain a column of smoke for a long time."

Chaiten, also located in the south, erupted during Bachelet's first term as president (2006-2010), practically destroying the nearest town under a blanket of ash.

Several airlines have decided to suspend flights to and from the region's El Tepual airport, in Puerto Montt, not due to any directives from the civil aeronautics authority, but only as a precaution.