Obasanjo described the burning of scores of villagers as they gathered free fuel from the pipeline as "grave" and ordered an investigation into the cause of the blast, Radio Nigeria said.

Oil-region militants have targeted pipelines and other petroleum-industry infrastructure in Africa's oil giant, cutting production by a quarter. But there was no sign that Friday's fire on a ruptured pipeline was sabotage.

Gasoline gushing from the pipeline exploded as villagers scavenged for the highly volatile fuel. It appears some victims tried to flee the unfolding disaster only to be overtaken by flames spreading across the fuel slick.

More than 1,000 Nigerians have died in recent years when fuel they were pilfering from pipelines caught fire . . . and officials said it would likely happen again.

"Because this thing has happened many times before, we thought it would be a deterrent, but apparently it wasn't enough deterrent for these people who died, " said Lagos state health commissioner Tola Kasali, surveying the scene near Ilado, about 30 miles east of the main city of Lagos.

"Anywhere you have a pipeline in this country, you have this problem because people are greedy and they want quick money, " Kasali said.

It is not known what set the fuel ablaze.

By day's end, about 100 of the dead had been given a mass burial, and Kasali said cleanup efforts were to resume today.

He said the uncollected bodies posed a health risk to the millions of inhabitants of Lagos:

"We're concerned that if we don't [bury them quickly], we'll create a health emergency in Lagos since it happened by the shore and the water will just flow back into the city."

The pipeline was used to transport gasoline across the country for national consumption.

The impoverished people of Nigeria often tap pipelines, seeking fuel for cooking or resale on the black market.