Katla is Eyjafjallajokull's more active neighbour, and scientists believe that there may be a link between the two volcanoes.
This link has not been physically proven, explains Magnus Tumi Gudmundsson a geophysicist from the University of Iceland. A circumstantial, historical connection "is putting people's eyes on Katla," he says.
"We know of four Eyjafjallajokull eruptions in the past [dating back to AD 500] and in three out of these four cases, there has been a Katla eruption either at the same time or shortly after.
"By shortly, I mean timescales of months to a year.
"We consider that the probability of Katla erupting in the near future has increased since Eyjafjallajokull went."