The workers, members of the National Union of Petroleum and Natural Gas Workers (NUPENG) called a strike on April 16, protesting disciplinary action taken against five union executives, according to Joseph Akinlaja, a spokesman for the union.
Shell spokesman Donald Boham said the workers have held the hostages captive since April 19, refusing to allow them to leave the rig. He said company officials have been involved in negotiations with the workers.
No injuries or deaths have been reported and the number of strikers is unknown.
The strike has halted drilling operations on four rigs owned by the Houston-based company Transocean. The company, the world’s largest offshore drilling contractor, has obtained court injunctions ordering the workers to leave the rig, according to Reuters.
Transocean is drilling in the region on behalf of multinational companies Royal/Dutch Shell and Total/Fina Elf.
A decision by the company to ferry workers 25 miles between the rig and the shore in boats instead of helicopters also helped prompt the strike, according to Akinlaja. He said union officials have ordered the workers to stand down.
Nigeria is the world’s sixth largest oil producer and the fifth largest producer of oil imports to the U.S. The country produces up to 2.2 million barrels per day.
Nearly of all of the oil is produced in the Niger Delta. Hostage taking and compensation demands are not uncommon in the region, according to the Nigerian press. In March, fighting halted 40 percent of Nigeria’s oil production.
In recent weeks, some multinational oil companies have been forced to increase security, following threats by militants to destroy facilities.
Although militants are to blame for much of the unrest, activists also are fighting for environmental justice and resource control in the area.