MADRID (REUTERS) - The public prosecutor in the Spanish city of Castellon has opened an investigation into potential criminal liabilities after hundreds of unusual small earthquakes, possibly linked to a natural gas storage project, have shaken the Valencia coast.

Scientists say the earthquakes are likely triggered by natural gas injections at the 1.3 billion euro (S$2.2 billion) Castor underground gas storage plant, owned by Spain's ACS and Canada's Dundee Energy.

"We have opened an investigation after a meeting with other public prosecutors in the region," Jose Luis Cuesta, head prosecutor of the Castellon region, said on Friday.

The probe will try to determine the cause of the earthquakes and whether any party could be held accountable, Mr Cuesta said.

ACS declined to comment on the probe, as did Escal UGS, the ACS and Dundee consortium that operates the storage facility.

The government has shut down development of the project indefinitely and asked scientists to look into some 420 earthquakes apparently triggered by natural gas injections at the facility meant to store gas in a depleted oil reservoir next to a fault line.

"Given preliminary opinions by experts with whom we are consulting every day, there is a high probability of a direct link between the gas injections ... and the seismic tremors," Spanish Industry Minister Jose Manuel Soria told reporters after a weekly cabinet meeting.

He said that surrounding regions had activated earthquake contingency plans but at the lowest level given that experts do not think the situation presents significant risk.