ABUJA, NIGERIA - Nigerian authorities are investigating the deaths of at least 15 people in the explosion of an illegally tapped oil pipeline on Sunday, an often-deadly practice that has been going on for decades.

Police in the Rivers state, which is in the West African nation's southern delta region, told VOA by phone Wednesday that Iba community locals were scooping crude oil and refining it at an illegal site late Sunday when the explosion occurred.

Police spokesperson Grace Iringe-Koko said authorities removed 15 bodies, including that of a pregnant woman, from the site. Twenty survivors, including the owner of the illegal refinery, were taken to a local hospital with burns.

'We're investigating," Iringe-Koko said. "It was this illegally refined product they were scooping that caused this fire explosion. We documented photographs of the incident. Members of the public and parents should warn their wards not to involve in such activities.

"We're also trying to see if we can deploy more security to that place so that such acts will not continue,' she said.

Crude oil theft is a perennial problem in Nigeria - one of the Africa's largest producers. The illegal refining of crude, known as "oil bunkering," is rampant in oil-rich regions.

In April, the Nigerian Extractive Industries Transparency Initiative said Nigeria lost about 620 million barrels of crude oil valued at $46 billion between 2009 and 2020.

Nigerian authorities have been trying to address the problem without much success.

Faith Nwadishi, executive director of the Center for Transparency Advocacy, said authorities must take decisive security and legal action to end oil theft.

'The technology around refining of crude is not what the local people themselves are involved in," Nwadishi said. "It's a cabal of very knowledgeable people with resources that are able to do that. So, government really needs to look inward - the issues around impunity and corruption. Our legal framework is weak."

Nigeria is dependent on crude oil for more than 80% of its national revenue.

Authorities say oil theft is detrimental to the Nigeria's economy and national security, but Nwadishi said widespread poverty in oil-producing regions also plays a role.

'Over the years that we have taken crude oil from these communities, there has been little or no development," she said. "Those same communities do not have projects, infrastructure. The people don't have electricity, and every day they're faced with the issue about degradation that comes from oil production within their communities. So, people around communities now see it as a right to take part of this crude [oil].'

Oil and gas expert Emmanuel Afimia said that without better opportunities for locals, it will be difficult to tackle oil theft.

'Many of these villages along the pipelines know about these illegal refineries, but as long as the money keeps flowing into the owners' pockets and then it keeps circulating in the community, they would not want to rat out whoever is operating that structure," Afimia said. "So, having to depend on communities to report structures will not work.'

The United Nations says that, worldwide, stolen oil accounts for around 5% to 7% of the global crude oil and petroleum fuel market.

Last year, Nigeria awarded a pipeline surveillance contract to former militant Government Ekpemupolo, also known as Tompolo, and uncovered many large sites where oil was being siphoned.

But experts say that unless the deeper problem of corruption is solved or authorities begin to prosecute offenders, oil theft will continue to be a problem in Nigeria.