AMERICAN authorities have filed charges against two Hong Kong-owned investment firms they say preyed on Asian immigrants. Investigators believe more than 5,000 customers invested more than US$10 million (HK$77.2 million) with the companies. The civil charges were filed in a federal court in Los Angeles against Lida International Financial Data Inc. of San Gabriel, Worth Financial Data Inc. of San Francisco and their parent, Topworth International Ltd. of Hong Kong. The companies' assets were frozen on Thursday. The companies are accused of violating state and federal commodities laws by selling futures contracts on the unregistered spot market in Hong Kong. ''If the sales took place at all they were unregulated - not regulated in Hong Kong and not regulated by the Commodity Futures Trading Commission,'' said Department of Corporations spokesman Lindsey Kozberg. Federal, state and local investigators will be liaising with Hong Kong authorities to check whether the funds were sent to Hong Kong to buy gold, silver and foreign-currency contracts as customers were led to believe. Commodity futures contracts give holders the right to purchase or sell a specific amount of a given commodity at a specified future date. They help businesses to budget future expenditures but are also a way for investors to bet on whether prices will rise or fall. She said investors had complained of losing up to US$20,000 after being promised huge rewards with minimal risk. Calls to the businesses' San Gabriel and San Francisco offices have gone unanswered this week. The state and federal agencies obtained a temporary restraining order, receiver and orders freezing assets and preventing the destruction or alteration of books and records. The court papers were unsealed on Wednesday and served simultaneously with search warrants on the San Gabriel and San Francisco offices of Lida and Worth, which served as sales agents for Hong Kong-based Topworth. Ms Kozberg said investigators would decide whether to refer the case for criminal fraud prosecution after reviewing evidence seized in the searches. California Commissioner of Corporations Gary Mendoza described the case as ''a classic example of affinity group fraud'', with members of a minority group taking advantage of people of similar background. None of the three companies was trading on exchanges registered with the US commission, nor were their commodities brokers registered with that agency, Mr Mendoza said.