High school girls as young as 16 are being forced to sell sex on the internet by a group of their former fellow students, according to North Vancouver RCMP.

The girls have placed ads on the popular online classified site Craigslist, according to police.

At least 11 girls are being "pimped" out by four men who previously attended the same high schools in the Vancouver suburb, said RCMP spokesperson Cpl. Marlene Morton

A high school counsellor at a school some of the girls attended told police there were rumors circulating that former male students were recruiting girls and forcing them to offer to have sex for money, which led to the investigation.

Morton said when the girls placed the ads, they would say they were 18, thereby skirting rules on Craigslist to stop child prostitution. The ads would contain descriptions of the girls, price lists and sometimes photos.

Men Morton called pimps would act like the girls' boyfriends and buy them clothing, alcohol, drugs and cellphones.

"They were being told at a later date, 'Well, I'm not your boyfriend, and you've got to work off your debt to me,' and this is kind of where the cycle seemed to have been starting," Morton said.

RCMP and social service agencies in the area are working with the girls, but Morton said because of the pimps' intimidation of the girls, it has been difficult to get them to speak out against them.