Geologists and environmental groups are blaming hundreds of small earthquakes that have rattled Spain's eastern coast on a large offshore gas storage plant.
Spain's National Geographic Institute says more than 300 earthquakes have struck the Gulf of Valencia, a zone not normally known for seismic activity, in the past month.
The strongest, a 4.2 magnitude earthquake, hit in the early hours of Tuesday.
Ten earthquakes from magnitude 1.4 to 2.9 struck on Wednesday.
The Spanish Government last month halted an injection of gas into a giant offshore storage plant in the Gulf of Valencia to allow scientists to investigate.
However, it insists the plant is not to blame for the tremors.
About 100 million cubic metres of gas was injected into the plant, which opened in June, before its activity was suspended.