A total of 19,722 people were investigated in stimulant drug cases in 1997, 302 more than in the previous year, the National Police Agency said Thursday.The NPA said the figure is the worst this decade and declared that Japan is now in a third period of drug abuse. Drug abuse cases have increased partly because it has become easier to get drugs and youths, including junior and senior high school students, use drugs because it is fashionable, the agency said.According to the NPA, 26,834 drug cases were investigated in 1997, a rise of 210 over the previous year. A total of 171.9 kg of stimulants were confiscated in 1997, most of which are believed to have come from China, it said.The largest single seizure of drugs was made in April last year, when some 58.6 kg of narcotics were found aboard a North Korean freighter, it said. Of the people who were investigated over drug seizures, 7,817 were members of underworld groups, representing 39.6 percent of the total and falling below 40 percent for the first time.Minors questioned in connection with drug cases shot up by 11.1 percent from the previous year and totaled 1,596, topping the 1,500 level for the first time in 10 years, the NPA said. In the past, stimulants were distributed to users mainly by people connected with underworld groups. For the past few years, however, Iranians have apparently been purchasing drugs from underworld groups and are peddling them on the street, it said.