The financial watchdog will speed up its investigation into the alleged stock manipulation case amid investors' cry over unfair trading. Shares in five companies -- Dongil Industries Co., Manho Rope & Wire Ltd., Pangrim Co., Taihan Textile Co. and Dongil Metal Co. -- plunged by a daily-permissible 30 percent Wednesday, prompting the country's bourse operator, the Korea Exchange, to suspend their trading...