Although a Shell spokesman said the cause of the fire had yet to be determined, it was noted that two fires last year along the same pipeline "were caused by sabotage."

Militant and criminal groups are often blamed for illegally tapping into pipelines in the delta and stealing oil and gas for personal use and resale on the black market. A chronic electricity shortage in energy-rich Nigeria has forced many to rely on generator power. Those who can't afford to pay premium prices for fuel often turn to the black market for sharply discounted gas.

Many Nigerians blame former President Olusegun Obasanjo for the country's woes saying his efforts to improve Nigeria's energy output were merely a coverup for eight years of graft.

Meanwhile, Shell officials noted the pipeline fires in the Ogoni province of Rivers state would not adversely affect production, nor would the company declare a force majeure, at least for the time being. While Shell expressed confidence it could eventually contain the fires that began burning Sunday, workers reportedly could not access either of the blazes, as locals living in the vicinity of the pipeline thwarted their efforts.

Their reluctance has prompted criticism.

"Clearly, if SPDC (Shell Petroleum Development Co.) had been allowed into Ogoni, these fires would not have been possible," read an editorial Wednesday in the Tide Online newspaper. "This is because some of the facilities would have been changed to avoid accidents while any systemic failure would have been addressed immediately to avert environmental crisis."

Similar reluctance to allow Shell workers to enter the region severely hampered production last year.

In January Shell shut down operations at its Forcados terminal following pipeline attacks that threw its 100,000 barrel-per-day production offline. The terminal had already been shut once before because of violence and reopened in October 2007 after more than a year of halted production. Since its reopening, the facility, which can produce some 450,000 barrels per day, had been operating at a fraction of its capacity.

And in July 2007 a leading Nigerian activist group called for Shell to shut one of its pipelines, saying the company has done little to control the fires that burned for several weeks.

The Movement for the Survival of the Ogoni People said fires have burned along the line since the previous month and were threatening several communities in the Niger Delta

Shell defended its actions, saying the company was trying to address the problem, but blamed residents of some communities affected by the fires.