HONG KONG — THE United States is battling an upsurge in Chinese organized crime that officials say threatens to worsen as Chinese syndicates flee Hong Kong to escape communist China's planned takeover of the colony in 1997.In a sign of growing concern, a US Senate delegation plans to visit Hong Kong next month on an unprecedented fact-finding mission to investigate how the Chinese crime groups operate and seek new ways to combat them. The delegation is scheduled to arrive in Hong Kong Jan. 5 for four days of talks before leaving for Taipei and Bangkok, which are also important bases for ethnic Chinese organized crime. The Senate probe follows hearings in Washington last month that documented a rapid expansion of Chinese syndicates engaged in heroin trafficking, money laundering, extortion, prostitution, murder, and other crimes in the US. "We believe the Chinese criminal organizations currently pose the most serious threat amongst all of the Asian criminal groups," Federal Bureau of Investigation (FBI) director William Sessions told the investigations subcommittee of the Senate Committee on Governmental Affairs on Nov. 6. Chinese criminal groups, while "small and disorganized" only a few years ago, are growing "exponentially in sophistication and power," US officials said at the hearings. One reason for the growth is the infiltration of overseas Chinese syndicates, or triads, which are forming close ties with established US-based Chinese crime groups, according to US and Hong Kong police. Some 50 triads are now operating in Hong Kong and Taiwan, the police say. The triads use more than 60 international routes to smuggle tens of thousands of Chinese citizens - including criminals from China, Hong Kong, and Taiwan - into the US, creating an explosion of illegal Chinese immigrants, US immigration officials say. An estimated 80,000 Chinese have been smuggled into the US from the Chinese coastal province of Fujian alone in the past two years. The smuggling of illegal immigrants is itself highly lucrative, with smugglers earning hundreds of millions of dollars. The would-be immigrants must pay an average of $30,000 in smuggling fees on arrival in the US. Often they become slaves to their creditors, working in sweat shops or as prostitutes, crime gang members, or drug couriers to pay off the smuggling fee. The Chinese groups tend to specialize in certain kinds of crime in big cities. Fujianese criminals in New York tend to be involved in violent crime. Cantonese from China's Guangdong Province operate vice and extortion rackets in San Francisco, and Taiwanese crime groups are active in money laundering and white collar crime in Los Angeles and Houston, according to US immigration officials. One Hong Kong triad, the Wo Hop Toe, is competing for the control of gambling and drugs in the San Francisco area, according to the FBI. The number of Chinese criminals entering the US is likely to increase when China assumes sovereignty over Hong Kong in 1997, officials predict. "A large number of Chinese - including Chinese criminals - undoubtedly will flee the closed communist government and move into the United States where they can operate more freely," warned Mr. Sessions. Some Hong Kong triad chiefs, known as "dragon heads," are even trying to take advantage of a new visa category that permits immigration by individuals who invest $1 million in the US, US immigration officials say.