Federal prosecutors in Kansas City this afternoon detailed their first-in-the-country use of a commercial sex trafficking law to go after would-be customers instead of those selling minors for sex.

Seven men, including four indicted by a federal grand jury today, now have been charged since Operation Guardian Angel began earlier this year.

The men allegedly responded to online ads placed by investigators offering 11 and 15-year-old girls for sex. Authorities arrested the men after each traveled to an undercover location to meet a girl.

The operation is a partnership between federal agencies and Kansas City and Independence police departments as part of the human trafficking rescue project.

Those charged face minimum sentences of 10 or 15 years in federal prison and could face up to life.

The defendants include an active duty recruiter for the U.S. Navy, a local businessman, a truck driver and a finance manager at a Mississippi auto dealership.

The first indictments were handed down last month against three Kansas men: Steven E. Mikoloyck, 47, of Overland Park; Ryan S. Doerr, 33, of Silver Lake, near Topeka; and Jimmy “Steven” Johnson, 22, of Olathe.

The attorney representing Mikoloyck and Johnson did not respond to an interview request. Doerr’s lawyer declined to comment while the case is pending.

Shane A. Childers, 32, assigned to the U.S. recruiting office in Lenexa, was charged in a complaint filed Friday. The Mississippi man, Christopher M. Cockrell, 33, was charged Monday. Childers did not yet have an attorney, according to court records, and the attorney representing Cockrell did not respond to an interview request.

A grand jury indicted both of those men today along with two others: Steven C. Albers, 40 of Kansas City and Richard J. Oflyng, 31, of Ottawa, Kan.

Investigators said that after placing the ads on Craigslist they were “inundated” with responses.

According to court documents filed to support charges against Cockrell and Childers, undercover officers received e-mail responses allegedly from both within minutes of posting an ad last Thursday.

The documents detail e-mail exchanges and phone conversations between the men and undercover officers in which they discuss the ages of the girls, how much it would cost for various sex acts and where to go to meet them.

When the men requested photographs of the girls, authorities sent pictures of actual law enforcement officers when they were 11 or 15, according to the documents.

Childers, who was wearing part of his Navy uniform, was arrested Thursday after he arrived at undercover residence in Kansas City. He allegedly had arranged to have sex with the 11-year-old girl for $80.

After his arrest, he told police that he intended to “save the girl” and get her out of the house, but then admitted that he had intended to have sex with her, according to the court documents.

Cockrell allegedly agreed to pay $60 for 30 minutes with the 15-year-old and said he would pay an additional $20 if he didn’t use a condom.

Officers provided an address for him in Kansas City. On Sunday afternoon Cockrell parked his pickup truck in the driveway and was greeted at the door by an undercover investigator.

Once inside, he allegedly handed the officer $100 and told him to keep the change. After being arrested, he admitted that he had intended to have sex with the 15-year-old girl who he believed was a runaway who was being “pimped out,” the court documents allege.