Ilado, Nigeria President Olusegun Obasanjo ordered stepped-up protection for pipelines after a gasoline blast killed up to 200 people, but Nigerians said impoverished villagers would keep tapping the pipes to pilfer fuel.
Rescue workers tried to finish collecting the dead for burial in mass graves by sundown. But at least 22 charred bodies floated in the tidal mangrove swamps east of the main city of Lagos - miles from the site of Friday's disaster in Ilado.
Police said there was no sign that the fire at a ruptured pipeline was sabotage, and they assumed villagers had punctured it to steal fuel. They said 150 to 200 people died in the flames when the gasoline ignited.
Obasanjo, who was on a state visit to Indonesia, ordered an investigation into the cause of the inferno, Radio Nigeria reported. He also called for increased protection of the country's vast web of pipelines, the radio said.
But Nigerians said little could keep poor villagers from rupturing the pipelines across the south of Nigeria because the allure of free fuel outweighs the well-known danger.
Villagers often tap pipelines to steal fuel for cooking or resale on the black market.
More than 1,000 people in Nigeria have died in recent years when fuel they were pilfering from pipelines caught fire.
"People are making so much money from selling stolen petrol that I'm sure they'll come back," said Hakim Bolaji, 32, a boat driver.
Nigeria, which normally pumps 2.5 million barrels of crude a day, is Africa's largest producer and the fifth-largest source of imports to the United States. Most of Nigeria's oil is pumped in the southern Niger Delta region, far from Lagos.