Spain's nuclear watchdog Monday called an extraordinary meeting of the heads of the country's nuclear plants to discuss safety issues following the latest incident at a reactor.

It also sent a team of investigators to the Vandellos II complex near Tarragona in northeastern Spain, where an electrical generator fire broke out on Sunday.

The Spanish Nuclear Safety Authority (CSN) said the fire was extinguished with no injuries or environmental damage reported.

It gave the incident a preliminary classification of zero on the seven-tier international scale of nuclear incidents, saying the plant's managers had followed the correct procedures.

The environmental group Greenpeace said the fire was caused by a leak of hydrogen, which exploded on contact with the air.

Vandellos II, which will now be closed for several weeks, had already been hit with record fines for its safety record.

And the incident came just weeks after the CSN pressed for a fine of nine million and 22.5 million euros (33.3 million dollars) against another plant, Asco I, also in Tarragona, over its handling of a radioactive leak for which some 2,600 people had to be screened.

The CSN said Monday it had summoned the committee in which the owners of all the nuclear plants are represented "to follow up on the latest incidents and look at plans of action."

The CSN holds three regular meetings per year — in April, July and November — but the November session would now be moved up to September.

Vandellos II is jointly run by the Spanish energy groups Endesa and Iberdrola. It was built in 1980 and has a permit to run until 2010.

Prime Minister Jose Luis Rodriguez Zapatero's socialist government has vowed to gradually close down the country's six nuclear power stations.

Spain is moving towards being a leading producer of electricity from renewable sources like wind and solar power.

But with oil prices soaring, the government is under pressure from some quarters to review its anti-nuclear energy policy.

Nuclear power, much of it imported from neighbouring France, provides around 20 percent of Spain's electricity needs.