Twenty minor earthquakes last night and some 300 in the last two weeks along Spain’s eastern coast have led to the government blaming a big offshore gas storage project using the pumped-out underwater reservoir beneath a former oil rig.

One tremor in the Bay of Valencia on Tuesday was of 4.2 magnitude: the gas storage project was halted just days ago.

“It looks that there is a direct relation between the injection of gas into the underwater storage cavity 22 kilometers offshore, and the micro earthquakes we have sufferered over the last 15 days,” said Spain’s Industry Minister José Manuel Soria.

Within range if any serious earthquake were to occur at the Castor plant is the Vandellos nuclear power station, and a number of populated areas. While a 4.2 strength tremor is no big deal, it is the strongest ever recorded in a region not noted for seismic activity.

People living opposite the Castor site are beginning to worry. Spanish environmentalists, who have campaigned against the European Investment Bank-supported project since 2007, said despite their demands no seismic study had ever been made, and that the plant was built near a fault line.