PESHAWAR: A worker was killed and four others were injured in an explosion caused by chemicals in an arms manufacturing factory in the Small Industrial Estate on Kohat Road here on Tuesday. A police official said the chemicals were stored in an arms factory, which exploded due to hot weather. The roof of a portion of the factory caved in due to the explosion, killing Roman and injuring four others. The police arrested Ajmal, the owner of the factory, and started an investigation.