Seven people have been arrested in the United States on charges of trafficking in endangered rhinoceros horns, federal officials said.

The most recent arrest took place Wednesday night when Jin Zhao Feng, a Chinese national, was taken into custody at Los Angeles International Airport, Thom Mrozek, a spokesman for the U.S. attorney's office, said Thursday.

Authorities suspect him of overseeing the shipment of dozens of rhino horns from the U.S. to China.

The arrests were the result of an 18-month investigation that was called "Operation Crash" — the term for a herd of rhinoceroses — and scrutinized an international smuggling ring that trafficked in sawed-off rhinoceros horns. The horns are used by some cultures for ornamental carvings, good luck charms or believed medicinal purposes, including cancer.

"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 S. Moreno, assistant attorney general for the Justice Depatment's Environment and Natural Resources Division.

Spike in rhino poaching threatens survival of species

All species of rhinoceros are protected under U.S. and international law, and all black rhinoceros species are endangered, federal officials said.

Rhino horns are composed of keratin, the same type of protein that makes up hair and fingernails. Rhinoceros horn is a highly valued and sought-after commodity despite the fact that international trade has been largely banned since 1976.

According to a report by NBC's Rock Center, an average-sized rhino horn in Vietnam can sell for as much as a quarter of a million dollars, which makes rhino horn gram for gram more valuable than gold or cocaine.

The arrests were initially reported by the Los Angeles Times.

Three of the alleged traffickers caught in Southern California were Jimmy Kha, 49, his girlfriend Mai Nguyen, 41, and Kha's 26-year-old son Felix. Each faces four counts of rhino horn trafficking in violation of federal laws protecting rare and endangered species.

Investigators reportedly seized several rhino horns, more than $1 million in cash, $1 million in gold bars, diamonds and Rolex watches during the raids, NBCLosAngeles.com reported.

One of the alleged suppliers, Wade Steffen, was arrested in Hico, Texas, and charged in Los Angeles, federal prosecutors said.

The Khas began receiving packages from Steffen and another alleged supplier in 2010. Seventeen packages were opened under federal search warrants and 37 rhinoceros horns were found, according to a criminal complaint filed in U.S. District Court in Los Angeles.

South African town dehorns rhinos in attempt to ward off poachers

A search of Steffen's luggage at the Long Beach Airport on Feb. 9 turned up $337,000 in cash.

According to NBCLosAngeles.com, the rhino horns seized as part of the raids were reportedly destined for buyers in Vietnam and China.

In New Jersey, Amir Even-Ezra was arrested Feb. 18 on a felony trafficking charge after purchasing rhino horns from a New York resident in New Jersey.

Antiques expert David Hausman was charged in U.S. District Court in Manhattan with illegally trafficking rhinoceros horns and with creating false documents to conceal the illegal nature of the transaction, prosecutors said.

The Associated Press contributed to this report.

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Workers hold a rhino during a media demonstration at the Rhino and Lion Nature Reserve outside Johannesburg, South Africa, on Thursday. The rhino later died.

A conservation group demonstrating an anti-poaching method for reporters in South Africa accidentally killed the rhinoceros they were using in the demonstration.

The rhino, nicknamed Spencer, went into convulsions and died after he was shot with a tranquilizer dart in front of a crush of TV cameras and photographers who had been invited to document an operation to insert a poison capsule into his horn.

The private reserve near the capital, Pretoria, calls in veterinarians to sedate rhinos so their horns can be treated with a dye and an insecticide, and tracking and identification devices can be inserted.

A male in his mid to late 20s, fairly old for such an animal, could not be revived after being sedated Thursday, said Rhino Rescue Project spokeswoman Lorinda Hern.

"The rhino had an unfortunate reaction to the anesthesia," she said. "Every time you dart a rhino, you take a risk that the rhino might not wake up and unfortunately today was one of those days."

Conservation groups insert poison capsules into the horns of rhinos, which release poison into the horn when it is removed from the animal and are meant to render the horn value-less for hunters seeking to sell it on for use in traditional medicine.

Conservation groups sometimes remove horns from rhinos to deter poachers, as msnbc.com's Dara Brown reported in the video below. The horns are similar to hair or fingernails, and grow back after several months. 

Both anti-poaching procedures require the rhinos to be sedated.

A decade ago South Africa, with more than 20,000 rhinos, was losing about 15 animals a year to poachers. But poaching has increased dramatically since about 2007 as the spread of wealth in places like Vietnam and Thailand has enabled more people to buy rhino horn, which is believed to have magical or medicinal properties in some cultures.

A record 448 rhinos were killed by poachers last year in South Africa, home to the greatest number of the animals. The number was up sharply up from 122 in 2009 and 333 in 2010, according to a report by AllAfrica.com. A majority were killed in the Kruger National Park, which borders on Mozambique, the report said.

"It's sad for us; it's the loss of another animal," Hern said, referring to the rhino's death. "It's a death that I still chalk up to poaching."

Msnbc.com staff and Reuters contributed to this report.

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