An industrial dispute in Suez triggered clashes between the police and workers who broke into a government building on Tuesday, setting fire to furniture, security sources and workers said.
Factory workers at Ceramica Cleopatra, a privately-owned firm, had gathered outside government offices in the port city to demand the authorities intervene to resolve their dispute.
As tempers flared, the workers hurled stones at the building of the Suez Security Directorate and raided the provincial administration office. Police used teargas to disperse the dispute, the sources said, speaking by telephone from Suez.
Many Egyptian workers have gone on strike demanding better wages and conditions in the 18 months since Hosni Mubarak was removed from power, emboldened by new freedom to protest.
The workers said the factory had been closed for nine days following a wave of strikes, but was meant to resume work on Tuesday according to an agreement with the owner, who had said he would negotiate with the workers once they were back at work.
The protests erupted when the buses which usually ferry the workers to the factory failed to show up, fuelling speculation the management had reneged on the agreement.
Ceramica Cleopatra, one of Egypt's biggest ceramics firms, has been hit by intermittent strikes for months as factory workers complain of low wages.
Suez, located at the southern entrance to the Suez Canal, was the scene of early and intense clashes between government security forces and protesters during the uprising that ousted Mubarak.
Al-Masry Al-Youm reported that the Third Field Army sent additional forces to the headquarters and the security department as violent clashes continued.
Ahmed Salah al-Din, deputy head of the trade union committee at Ceramica Cleopatra, said the police arrested six workers while 15 others were injured and suffered breathing problems after the police attacked them with batons and tear gas.
Al-Masry Al-Youm reported that cartridges were found in the area, but the source remains unknown.
Suez Governor Mohamed Abdel Moneim Hashem, meanwhile, asked employees to leave the building due to the clashes.