At least 37 people have died after being exposed to toxic fumes while allegedly collecting petrol from a pipeline in Rivers State, Nigeria, with more people still feared missing after a large group gathered at a jetty under the cover of darkness.
The deaths were reported after more than 100 people travelled in small boats to Okari Jetty in Okrika to collect the refined fuel, according to the Youths and Environmental Advocacy Centre (YEAC), an environmental group operating in the oil-rich region.
YEAC said its network of volunteers and human rights defenders reported that several people in Okrika died after inhaling fumes from what is locally known as "Indorama fuel".
The fuel is a refined petroleum product known as PMS, or Premium Motor Spirit.
Many people are still missing following the incident, according to YEAC. Local reports said some of those affected collapsed, with some falling into the Bonny River while others were taken to hospital for treatment.
Police told the BBC that investigations were still under way to establish the exact number of people affected and determine what happened during the incident.
The incident happened in Rivers State, one of the states that form part of Nigeria's southern Niger Delta region.
The Niger Delta is a large area of swamps and wetlands along Nigeria's coast and contains major reserves of oil and gas.
Oil theft has remained a major problem in the region for decades. Criminal groups have been known to tap pipelines and move crude oil and other petroleum products into boats and storage tanks.
The stolen products are then sold on the black market or taken to illegal refineries.
The latest incident has again drawn attention to the dangers linked to illegal oil tapping and the collection of petroleum products from pipelines.
The Nigeria Security and Civil Defence Corps (NSCDC) has called on the public and media to depend on verified information as security agencies continue efforts to establish exactly what happened in the early hours of Thursday.
The NSCDC also condemned the illegal tapping and siphoning of petroleum products, warning that such activities put lives, the environment and the economy at risk.
Campaigners have also linked oil theft to environmental damage in the Niger Delta, where years of oil-related activities have affected communities and the surrounding environment.
The Nigerian government has increased operations against oil theft in recent years as it seeks to protect the country's oil industry and improve production.
On Thursday, the director of naval information, Capt Abiodun Folorunsho, warned oil thieves that they had "no hiding place" from the navy, which carries out patrols along the waterways and coastal areas of the Niger Delta.
"Their days are numbered, and if we catch you, of course, we'll ensure that you face the law," he said in an interview with Nigerian broadcaster Channels TV.
The Nigerian navy has increased maritime security operations in the region, while the military and other security agencies have also carried out operations targeting oil thieves.
Those involved in oil theft often operate from the area's dense mangrove forests, making it difficult for security agencies to track them down.
Nigeria is also seeking to increase its oil production after years of challenges linked to theft, insecurity and underinvestment in the oil sector.
The country has set a target of raising oil production to about three million barrels per day by 2030 and is counting on improved security and reforms to attract new investment.