BEIJING, Sept. 12 -- The number of smuggling cases declined last year but there was an increase in the number of serious cases, a senior Customs official has warned.     Customs across the country uncovered 19 serious cases last year -- each involving at least 100 million yuan (13.2 million U.S. dollars) worth of products -- compared with 13 such cases in 2005, Xia Shouda, deputy director of the anti-smuggling bureau of the General Administration of Customs, said.     He said the 19 cases - out of last year's total 7,240 smuggling cases -- involved 9.35 billion yuan (1.24 billion dollars), accounting for about 70 percent of the total value of products in all cases.     Administration figures also show that the number of smuggling cases last year dropped by 60 percent from 2004, but the value involved was up by 75 percent to 13.7 billion yuan (1.8 billion dollars).     The figures for this year are unavailable.     "Although our efforts to combat smuggling have achieved some success, the overall situation remains grave. In some places, it could be critical," Xia told China Daily.     Coastal areas were the most heavily hit, according to Xia. Eight of the 19 cases last year were in South China's Guangdong Province; the rest in eight coastal cities and provinces including Shanghai, Qingdao, Tianjin, Hainan and Fujian. In 2005, only six coastal cities and provinces had such cases.     The biggest case reported was in the southern city of Shenzhen, where a smuggling group trafficked more than 2 billion yuan (263 million dollars) worth of cigarettes from 2003 to last January. About 20 people are on trial for smuggling.     Xia said that behind the mass smuggling cases - mainly involving cigarettes, food, cars, raw materials, metal scrap, mechanical equipment and cattle hides - were usually well-organized groups, which sometimes resort to violence. "We've encountered at least 10 such violent cases so far this year," he said, without giving any casualty figures.     The deputy director also revealed that international drug trafficking groups are increasingly targeting China as a transit point and consumption market.     Customs last year seized 798 kg of drugs in 330 smuggling cases, up 61 percent and 86 percent.