THREE KILLED IN SOUTH AFRICA ZINC REFINERY CLASH Three black workers were killed and seven injured in fighting at a South African zinc refinery last night, Gold Fields of South Africa Ltd said. The company said two groups of workers began attacking each other at about 1000 local time with machetes, knives and sticks at a hostel at the Zincor plant, some 40 kms east of Johannesburg. It said the fighting was "quelled" after 25 minutes by its own security staff. Police were called but the fighting had ended by the time they arrived. A company spokesman said he had no idea of the cause of the fighting. An investigation was underway, he said.