Two people were still missing in Nigeria’s oil-rich southern delta region on Saturday after a pipeline explosion that killed 12, police said.

“Twelve persons were burnt beyond recognition, including a soldier on guard duty amongst others,” said Bayelsa state police spokesman Asinim Butswat.

“Four persons were rescued alive and are undergoing treatment while two persons are still missing. Search for the missing persons is still ongoing.”

The blast happened at about 4:00 pm (1500 GMT) on Thursday on the Tebidaba-Clough line in Azuzuama, in the Southern Ijaw area of Bayelsa.

Staff from Italian energy giant Eni’s Nigerian subsidiary Agip were carrying out repairs at the time after a recent oil spill.

Eni said in a statement on Friday that the pipeline had been damaged by sabotage.

Oil spills are a major hazard in Nigeria and in March, Amnesty International claimed that Agip and Anglo-Dutch Shell had reported 553 spills in 2014.