MADRID -- Firefighters had put out the flames in all but one of seven blazing fuel tanks at a Spanish refinery by late Friday as the death toll from an explosion and fire at the plant rose to five, officials said.

A spokeswoman at Madrid's La Paz hospital said a 20-year-old man who suffered severe burns in Thursday's explosion at the Repsol YPF refinery in Puertollano died on Friday evening.

A middle-aged refinery worker died earlier on Friday at La Paz hospital while another three workers died on Thursday.

Five other badly burned workers, in serious or critical condition, remained in two Madrid area hospitals.

Some 400 firefighters have battled since Thursday to extinguish the blaze in seven tanks containing 8,600 cubic meters of gasoline. But black smoke could still be seen rising on Friday evening from the refinery 240km (150 miles) south of Madrid.

Repsol said in a statement that firefighters had flooded the area with foam, putting out the blaze in six of the seven tanks. The seventh tank continued to burn but firefighters would attempt to douse the flames with foam "when conditions permit", it said.

The company said the blaze was under control and confined to the tank area.

Production at the 140,000-barrel-a-day refinery has been suspended since the explosion, which sent a dense plume of black smoke and huge flames billowing into the air.

Investigators could not begin probing the cause of the explosion until the fire was put out and there was no estimate yet of the cost of the damage, Repsol spokesman Manuel Hermogenes said.

A company source estimated on Thursday it could take about a week for the refinery to resume operations.

Spanish newspapers said it was the sixth accident in the last decade at the Puertollano refinery that have claimed a total of 13 lives.

Puertollano is one of five Repsol refineries in Spain and accounts for some 12 percent of its total refining capacity.

Oil traders said the shutdown would have only a minor impact on European oil product markets as the plant was not an export refinery and was already due for a month-long shutdown starting later this month.