Three Northern Virginia gang members pleaded guilty Thursday to sex-trafficking charges for prostituting young girls.

Two of the men were associated with the Underground Gangster Crips, a Fairfax County-based division of the Crips gang. The other was a member of the Manassas Park Locos clique of the SUR-13 gang.

All three face mandatory minimum sentences of 10 years behind bars and could receive up to life in prison.

The two Crips members were charged in federal court in Alexandria last month for an operation that authorities said targeted high school girls in Fairfax, recruiting them as prostitutes and intimidating them with threats and violence if they tried to quit. Three others were also charged, and 23-year-old Christopher Sylvia of Springfield and 21-year-old Michael Jefferies of Woodbridge will cooperate with prosecutors, according to their plea agreements read in court.

Sylvia admitted to working as a driver for the operation. Jefferies admitted to serving as a bodyguard, renting hotel rooms and posting an online advertisement to solicit customers.

District Judge Leonie Brinkema asked Jefferies what being a bodyguard meant."I protected the girls," he said. When the teenagers were with clients, he said, "I would watch over them."

The Crips had been recruiting girls online, at schools and at Metro stops for the prostitution operation since at least April 2009, according to court records. Court documents list 10 victims but prosecutors say they believe there are many others.

In court Thursday, Jefferies said he didn't know the girls were younger than 18. But under questioning from Brinkema before she accepted his guilty plea, he affirmed that he knew the girls were in high school and that the gang had recruited minors to work as prostitutes.

No other hearings have been scheduled for the other men charged in the case, 26-year-old Justin Strom, 27-year-old Donyel Dove and 23-year-old Henock Ghile. Court documents say girls were often coerced into having sex with Strom as a type of tryout, choked or beaten if they tried to quit and forced to ingest cocaine and other drugs.

In a separate case, SUR-13 member Ramiro Jamaica admitted to prostituting a runaway girl. Jamaica, 20, took in at least one girl who had run away and then slept with and prostituted her.

"I was trying to help her out," Jamaica said in court.

The victim told the FBI that she was forced to have sex and was once choked to the point that she became unconscious, according to court records.