LAGOS (AFP) - Striking Nigerian oil workers have threatened the lives of 97 British, American and European oil workers trapped on four hijacked oil rigs, hostages said. The men have been stuck on the four offshore platforms since the strike broke out on April 19 and are being held by an increasingly desperate crew of strikers, who have threatened to blow the rigs up, union sources said. "If these people start to think they have lost everything then they will no longer see a need to keep us alive," said one worker in an e-mail sent to his union and passed on to AFP. "If they have lost everything they well make sure that we lose everything, and that means our lives," he wrote. Around 100 strikers have blocked helicopter decks on the platforms, which are anchored in deep water south of Nigeria's Niger Delta. Workers who have been able to contact their families by telephone and e-mail say they are concerned that any attempt to retake the rigs by force could lead to a dangerous confrontation with the strikers. "Today ... the crew went mental. They flared up and are extremely angry at the thought the military people or armed people were going to come and forcibly remove them," a foreign worker said in another e-mail. "They threatened violence, in particular to blow up the rig... and kill everyone on board," it said. The rigs' owner, Transocean Inc, has hired four bailiffs, each with three armed police guards, to deliver injunctions to each of the platforms ordering an end to the protest, oil industry sources said. "If the bailiffs appear, the Nigerian workers have threatened to fight back," said Jake Molloy, general secretary of the international offshore workers' union, the Oil Industry Liaison Committee. The Nigerian strikers' union, the National Union of Petroleum and Natural Gas workers (NUPENG), told AFP that they did not support the action, which began after five workers were sacked for theft. But NUPENG general secretary Elijah Okougbo said that they had been unable to persuade the men to end their protest. A spokeswoman for the British foreign ministry told AFP that 97 expatriate workers were on board the four rigs, including 35 Britons. A diplomat in Abuja told AFP that 21 US citizens were among those trapped. Molloy said 34 workers had been allowed off the platforms on Monday in a goodwill gesture from the strikers, but added that the threat to send bailiffs to enforce an end to the protest had raised concerns. "The wives are very concerned," he said. "Transocean had an opportunity to end this strike by offering a reasonable severance package to the workers, but they seem to want to tough it out." The rigs -- the Sedco 709, the MG Hulme, the Trident 8 and the Trident 6 -- are operated by Houston-based Transocean in the Gulf of Guinea, in deep water off the eastern Niger Delta. Three of the platforms are leased to the Anglo-Dutch group Shell, and European workers are thought to be trapped with the US and British staff. "Transocean is continuing efforts to resolve the labour stoppage but cannot estimate the possible length of the strike or its financial impact," the US firm said in a statement Monday. A daily log of events on one of the rigs, the Sedco 709, tells of tensions rising as the dispute drags on. On April 25 two expatriate workers who suffered "nervous breakdowns" were medically evacuated from the platforms along with one worker whose wife was said to be in a critically ill, the log says. Nigerian oil facilities are often taken over by strikers or by local militants keen to extract lucrative concessions from the wealthy foreign companies that produce the country's sole profitable export. It is rare for expatriate staff to be hurt in these incidents. Last month violent unrest in the western Niger Delta forced three oil multinationals to suspend their operations, stopping more than 40 percent of Nigeria's daily exports of crude. Nigeria is the world's sixth largest oil exporter, with an OPEC quota of more than two million barrels per day. **PHOTO CAPTION*** Workers on an oil rig in Nigeria. Striking Nigerian oil workers have threatened the lives of 97 British, American and European oil workers trapped on four hijacked oil rigs.(AFP/File)