The factory’s director, human resources director and two other bosses at the Åkers plant in Fraisses, southwest of Lyon, were detained on Wednesday by workers angry

over the shutdown and loss of 120 jobs.

After spending the night in a factory meeting room, the managers tried on Thursday to persuade the angry workers to let them go.

“There is no other solution than to let us out. The company directors have stripped us of our mandate to negotiate,” said factory director Laurent Dousselin.

A court in nearby Saint-Etienne ordered the immediate release of the four men but a justice official who turned up at the factory to meet with them was blocked from entering.

“No one has the right to treat us like trash and get rid of us with just 6,000 euros (8,500 dollars),” said one worker.

Union officials said they were demanding a lay-off package of 28,500 euros for each worker but the managers said the Swedish headquarters were refusing to negotiate while the bosses were being held.

French industry minister Christian Estrosi backed Åkers, saying “there can be no dialogue until the managers have recovered their full freedom”.

Åkers announced three months ago that it planned to shut down the Fraisses plant in June, citing a collapse in customer orders.

Workers drank coffee and ate sandwiches outside the plant on Thursday and bitterly complained that they were not being compensated sufficiently for their loss of income.

“They shouldn’t take us for naive fools,” said Ludovic, a maintenance worker.

French workers last year carried out a series of “bossnappings” to protest layoffs, but no such radical action has been taken over the past months.

President Nicolas Sarkozy in April spoke out against the detentions, saying there were illegal and vowed to take action.