Over 100 Nigerians were killed in an explosion at an illegal oil refinery in the southeastern part of the country on Saturday, Reuters reported. The refinery was located in a forest area on the border of Nigeria’s Rivers and Imo states.

“The fire outbreak occurred at an illegal bunkering site,” said Goodluck Opiah, Imo commissioner for petroleum resources, according to Reuters. “Over 100 people were burnt beyond recognition.”

The immediate cause of the explosion and the extent of the deaths, injuries and damage were being investigated, said State Commissioner for Information Declan Emelumba, the Associated Press reported.

Illegal refining of crude oil is a common sight in Nigeria. Here, thieves often vandalise pipelines owned by major oil companies to steal crude oil which they refine to sell on the black market, according to Reuters.

The thieving process has caused several fatal accidents and has polluted a region that already suffers from oil spilling into farmland, creeks and lagoons, The Guardian reported.

In Saturday’s explosion, several vehicles that were in a queue to buy illegal fuel were burnt, the Youths and Environmental Advocacy Centre said

In October, at least 25 people, including children, were killed in an explosion at another illegal refinery in Rivers state, according to Reuters.