The chairman and managing director of a Corinth pipe construction factory were arrested in Athens yesterday following Thursday’s fatal explosion that killed six workers. Corinth Pipeworks Chairman Athanassios Mitropoulos and his son Constantinos, the company’s managing director, were to be charged late yesterday in Corinth. The factory manager and another four officials were arrested on Thursday, shortly after the accident. Yesterday, Labor Ministry officials said the blast appeared to have been caused by an oxygen or an acetylene cylinder in the factory’s welding section. Stelios Xiarchos, head of the ministry’s Labor Inspectorate (SEPE), said past inspections of the plant had found workers without any specialized training to be operating dangerous machinery. But he added that SEPE had no authority to temporarily close down factories for such infringements. The six victims were buried yesterday in Corinth, where labor unions held a protest strike. Meanwhile, three employees injured in the blast were in stable condition in hospital.