The Hague - The British-Dutch oil giant Shell said it was shutting down Europe's biggest refinery after a pre-dawn fire broke out at a power station on the vast site on Sunday.Flames billowed into the sky over the port of Rotterdam after the blaze erupted at a high-voltage power station at the Shell Pernis refinery. Firefighters brought the fire under control by around 06:00 (04:00 GMT)."Shell is in the process of shutting down all the units at the site," a Shell spokesperson told AFP.The units are all interconnected and "several of them are out of service due to the power outage caused by the fire," he said.It takes "hours, or even several days" each time that operations are closed down or restarted, he said.Shell did not confirm media reports that the fire may have been caused by a short circuit. Instead the company said it would "wait to know more about the circumstances of the incident."According to the regional security authority, there were no toxic materials in the smoke.Shell could not immediately disclose the extent of the damage, nor when the refinery would return to full capacity.The refinery covers the area equivalent to 800 football pitches, and its pipework, if laid end to end, would be long enough to circle the Earth four times.