KUWAIT CITY (AFP) - Four workers were killed and two employees injured in a gas pipe explosion on Saturday at Kuwaits largest refinery of Mina al-Ahmadi, Kuwait national refiner said. The explosion took place at the Gas Liquefaction Plant at the refinery during maintenance works, Kuwait National Petroleum Co (KNPC) said in a statement cited by the official KUNA news agency. The four people killed work for a private contractor, KNPC said. Two company workers were also injured but discharged from hospital after treatment. An industry source earlier told AFP the dead workers were Asians and that the explosion was caused by a gas leak, adding that the blast also wounded three firemen.