The Crips leader approached the 16-year-old on the Metro, federal prosecutors allege, told her she was pretty and broached an offer he and his associates would make to high school girls across the area: She could make a lot of money by having sex with men.

Flattered by the compliment, she was one of at least 10 teenage girls who became prostitutes for the Underground Gangster Crips, a violent street gang in Fairfax County, court papers say. The girls were recruited on Facebook, at bus stops and even in school, according to authorities, then forced to stay through threats and violence, including rape.

Justin Strom, 26, of Lorton is accused of leading the gang. He and four other alleged members have been charged with sex trafficking, according to documents unsealed Thursday in U.S. District Court in Alexandria. If convicted, each could serve life in prison.

Federal prosecutors said the operation was unusual because it preyed on girls living at home, not runaways, and used social media to lure teens from Virginia, Maryland and West Virginia. At least one teenager was recruited at school by a classmate who was working as a prostitute, authorities say.

“There’s no high school that’s immune to this possibility,” said Ken Cuccinelli II (R), Virginia’s attorney general, at a news conference. “This is a problem — thanks to the Internet — that can reach across borders more easily.”

Strom’s attorney, Alan H. Yamamoto, said Thursday afternoon that because he had just learned about the case and had not met with his client, he would not comment on the charges.

In recent years, street gangs have turned to prostitution as a moneymaker, authorities said. Members of the violent gang Mara Salvatrucha, known as MS-13, have been accused in federal court in Virginia of prostitution-related charges involving juveniles.

Neil H. MacBride, U.S. attorney for the Eastern District of Virginia, said Strom and his associates are accused of posing as a woman named “Rain Smith” on Facebook and sending more than 800 messages to girls they found attractive to lure them into the ring. Strom instructed a 17-year-old runaway, who was the gang’s most senior prostitute, to help find others, court records say.

In November, that girl, identified in court papers as M.W., approached a classmate at an unnamed school and told her she was a “confident pretty woman.” M.W. also chatted her up on Facebook:

“M.W.: Lol u tryna make sum money . . . ?

Girl: Howww

M.W.: Trickin . . . Like u get 50% n u get all da drugs . . . uwwant basically.”

The classmate became part of the ring, earning $100 per client, according to court records. Other girls were often required to submit to sex with gang members as a “try out,” before they could join the operation, court records say.

The teens were advertised on Web sites such as Craigslist and, according to court records, and the prostitution allegedly occurred in Strom’s Lorton home. At other times, the victims were taken to “out calls,” sometimes driven in one gang member’s white, four-door Cadillac. The girls also worked door to door at apartment complexes in Northern Virginia, court documents say.

On one such trip, M.W. and another girl had sex with 10 to 15 men, charging them each $30 for 10 minutes, according to court records. Afterward, the girls met up with Strom, bought PCP, ecstasy and other drugs, and partied, court records say.

If the girls refused to work, it sometimes turned violent. Strom made an 17-year-old girl he was recruiting use cocaine, cut her arm with a knife and forced her to have sex with him, according to court records. The girl was then taken to an apartment, where she was forced to have sex with 14 men, court documents say. Strom allegedly collected $1,000 that night.

While Strom ran the operation, other gang members served as bodyguards and drivers, court papers say. Michael Tavon Jeffries, 21, of Woodbridge; Donyel Dove, 27, of Alexandria; and Henock Ghile, 23, and Christopher Sylvia, 22, both of Springfield, were arrested over the past several weeks. Attorneys for the men did not return requests for comment.

Officials said that the ring might have been in operation for as long as five years but that authorities began investigating it in November. The investigation was a joint operation of Fairfax County police, the FBI and the Northern Virginia Human Trafficking Task Force.

It was not clear how the ring unraveled, but court papers say that in November, M.W. told a staff member at her school that a man had been paying her to have sex with people and that “she was not sure what to do.” The next day, the documents say, the teenager was interviewed by investigators and said she did not need help and was “living the life she chose.”

Officials also said they were contacted by a parent who had questioned a daughter and learned she had been working as a prostitute for the gang.

The Underground Gangster Crips are a subset of the Crips gang, which formed in Los Angeles in the late 1960s and early 1970s, authorities said. The gang operates in the Washington region, officials said. It has a long and violent history in Fairfax County, allegedly committing rapes, armed robbery and selling drugs, according to court documents.

Authorities said the case should be a warning to parents to be vigilant about their children’s activities on social media sites.

“This type of crime is insidious in its nature,” said Ronald T. Hosko, special agent in charge of the FBI’s Washington Field Office. “It leaves profound psychological scars on its victims.”

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