US officials have announced the arrest of seven people in a crackdown on the illegal global trade in endangered black rhinoceros horns. Arrests were made across the country over recent days in \"Operation Crash,\" which involved multiple law enforcement agencies, the US Department of Justice said in a statement on Thursday. A Chinese citizen, Jin Zhao Feng, was arrested in Los Angeles and is accused of shipping dozens or more rhino horns to China. The horns are used in traditional Asian medicine, regardless of fears that poaching is driving the huge African animal to extinction. Also arrested were four alleged members of a US-based trafficking ring that supplied Feng with the horns. They were charged with conspiracy and violation of laws protecting endangered species. Searches of one of the alleged suppliers, Wade Steffen, who was arrested in Texas, turned up 37 rhino horns, as well as $337,000 in cash, US officials said. Additional searches by agents pointed to the lucrative nature of the illegal business. \"Agents found rhinoceros horns, cash, bars of gold, diamonds and Rolex watches. Approximately $1 million in cash was seized and another $1 million seized in gold ingots,\" the statement said. Another two men were arrested in the sweep, one of them in New Jersey after he allegedly purchased horns, and another, an antiques expert, in New York, where he was charged with trafficking horns and creating fake documents. The antiques expert, David Hausman, allegedly purchased a taxidermied rhinoceros head from an undercover officer \"and was later observed sawing off the horns in a motel parking lot,\" the Justice Department said. \"The rhino is an animal of prehistoric origin that is facing possible extinction because of an illegal trade for its horns on the black market that is driven by greed,\" said Ignacia Moreno, assistant attorney general for the environment and natural resources division of the US Justice Department. \"The rhino is protected under both US and international law, and we are taking aggressive action to protect the rhino by investigating and vigorously prosecuting those who are engaged in this brutal trade,\" Moreno wrote.