Twelve people died and three were injured in an explosion during repair work at an Eni SpA crude oil pipeline in Nigeria.

The victims worked on a maintenance team for a local service company, Rome-based Eni said in a statement Friday. The Tebidaba-Clough Creek pipeline in the Niger delta was previously “damaged by acts of sabotage.” The company said it is still investigating the cause of Thursday’s blast.

Accidents are common in Nigeria, where pipelines are often breached in attempts to pilfer crude. The incidents interrupt oil and gas flows, affecting Nigeria’s energy exports and revenue for companies including Eni, Royal Dutch Shell Plc and Chevron Corp. Thursday’s incident was the worst since January 2012, when an explosion at Chevron’sFuniwa gas field killed two workers, according to a spokesman for a local environmental group.

Eni had 13 incidents related to pipelines and oil wells in Nigeria in May including theft, pipelines being cut using a hacksaw and equipment failure, according to the company’swebsite. Seventeen were reported in April and 14 in March.

Hundreds have been killed in Nigerian pipeline accidents in the past decade. An explosion at a vandalized oil pipeline in Lagos, Nigeria’s largest city, started a fire that killed at least 200 people and burned many more in December 2006. In May that year, about 200 people were killed when another oil pipeline exploded near Lagos.

Nigeria, Africa’s biggest oil producer, loses an estimated 300,000 barrels a day to criminal gangs that tap crude from pipelines that criss-cross the southern, oil-rich delta for local refining or sale to tankers waiting offshore, according to state-owned Nigerian National Petroleum Corp.

Source: Bloomberg