Taipei - Taiwan has seized a stash of amphetamines worth more than $11.3m hidden in frozen tuna cargos at Kaohsiung port, the largest smuggling case of the drug bound for Japan, officials said.The two containers headed for Japan's Shimizu port held 138kg of the drug which was hidden in plastic bags and stuffed into the bellies of the fish."A customs officer found shadows in the belly of one of the tuna during a detailed scan," the Ministry of Justice Investigation Bureau said in a statement. So far three people have been detained in connection with the case, according to the bureau.Investigators had earlier received intelligence that a refrigeration company in southern Taiwan was involved in smuggling drugs. All of those arrested work for the refrigeration company.The statement said amphetamines are almost indiscernible from crushed ice after freezing and an X-ray scan initially failed to detect the hidden drugs. The price of amphetamines has surged in Japan almost 60% in recent years, it added. Authorities are still investigating the origin of the drugs and possible accomplices.