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Mysterious: UFO spotted at the eruption site of the Calbuco volcano
Footage captured at the Calbuco volcano eruption in Chile has caused controversy - after viewers spotted a 'UFO' in the sky among the plumes of dust and ash.

The unidentified flying object appears to hover in mid-air to the left of the eruption for a few seconds, flashing against the ash filled sky.

Moments later, the mysterious object disappeared.

The clip was uploaded to YouTube on April 23 by Ana Luisa Cid and has already clocked up more than 200,000 views.

Ana wrote: "Luminous object near the plume, captured on 22 April 2015.

"Some believe it may be a drone or a police helicopter.

"What is striking, in my opinion, is that the object remained static, then vanished."

Calbuco, like 90% of all volcanoes, lies within the "Ring of Fire", where tectonic plates converge along the edges of the Pacific Ocean.

The plates are rock slabs which make up Earth's surface, floating on a layer of molten rock under the crust.

Eruptions happen when gas dissolves under pressure within magma, until it cannot be contained.

Calbuco had lay dormant for 40 years but dramatically erupted into life - the first on Wednesday afternoon followed by a second powerful blast.

Mr Rothery said: "When then tectonic plates move it creates gases which then bubbles to the surface sparking the eruption.

"It's a bit like shaking a can of beer and when you pull the tab, it foams up."

The Calbuco volcano is one of the most active in Chile but its eruption took officials in the area by surprise.