The Canary holiday island of La Palma has recorded dozens of mini-earthquakes over the weekend, scientists report.
More than 40 tremours were recorded in just 48 hours, all between 1.5 and 2.7 on the Richter scale.
However, the earthquakes took place at such depth under the sea that residents on the island did not feel them.
The largest of the tremours, which took place at 1pm on Saturday hit 2.7 on the Richter scale and was located at a depth of 17.4miles.
In the following hours, another ten tremours were recorded, taking the total of mini-earthquakes until Tuesday to 50, according to the National Geographic Institute (IGN).
La Palma is the most north-westerly island of the Canary Islands, and is home to some 86,000 people - a population which increases significantly during tourist season.
Like the other Canary Islands, La Palma is volcanic and is considered the most 'active' in the archipelago.
The most recent eruption on the island, which saw the Cumbre Vieja - 'Old Summit' - volcano erupt, took place in 1971.
The current event has been dubbed a 'seismic swarm', and while unusual, large numbers of these smaller tremours are not abnormal, the director of the IGN in the Canary Islands, María José Blanco, told Canarias7.
However, she added that they had "never recorded a similar swarm' since monitoring began on La Palma.
The IGN and the Volcanological Institute of the Canary Islands (Involcan) have increased surveillance on the island to monitor the increase in seismic activity.
A spokesperson for Involcan told Canarias7 that 'seismic swarms' are 'absolutely normal' for an active volcano. such as Cumbre Vieja.