For four months, Federal Way police sent two undercover detectives — a 29-year-old woman and a 33-year-old man — to infiltrate an area of increasing drug use:

High schools.

Officials provided few details Thursday on how the detectives, well out of their teens, were able to pass themselves off as students, but their undercover operation succeeded to an alarming extent.

With little difficulty, they purchased a cornucopia of illicit drugs — including marijuana, Ecstasy, cocaine and the prescription drug oxycodone — as well as rifles and semiautomatic handguns.

The investigation culminated Thursday with criminal charges filed against 12 students, ranging in age from 13 to 18, and against two adults not associated with Federal Way schools.

Ten of the individuals charged were arrested early Thursday. Three students and one adult were still at large Thursday afternoon.

Five of the 12 students charged attended Federal Way High School, four attended Todd Beamer High School and three attended Decatur High School.

The two undercover agents spent time at each of the three schools from January to April, but are no longer posing as students.

One of the adults implicated, Ryan Horne, 22, faces federal charges. In addition to allegedly supplying several different types of drugs to undercover detectives, Horne is also accused of selling the undercover officers five guns.

"Today's message should be very, very clear: We will not tolerate drugs or guns to be trafficked in our schools," said Mark Larson, chief criminal deputy of the King County Prosecutor's Office.

"Our schools and community are safer today as a result of our investigation," said Federal Way Police Chief Brian Wilson, who led the inquiry.

Agents from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives and the Drug Enforcement Administration also participated in the investigation.

Perhaps the most striking aspect of the case is the number of willing suppliers the undercover agents found in Federal Way schools, and the ease with which they found them. Charging papers filed in the case describe in detail the casual nature of many of the transactions.

One marijuana supplier named Joe made his first sale to an undercover officer during a third-period class at Federal Way High School in February.

"Joe told me to sit by him," the officer recounted in court papers. "Joe pulled out suspected marijuana from his pants pocket and in the middle of class and while the teacher was instructing took out $5 worth of marijuana to sell me. ... Joe did this behind his baseball hat in a poor attempt to conceal the transaction from the teacher."

Seven of the implicated students sold marijuana to the undercover officers, and four sold Ecstasy tablets.

Eleven of the students have been charged as juveniles because they are 17 or younger. The Seattle Times generally does not name juveniles charged with crimes.

A 12th student, Sarrel Kim, 18, was charged in King County Superior Court with delivery of marijuana and cocaine, possession of cocaine and possession of a stolen firearm. Kim sold the drugs and a .38-caliber Smith and Wesson handgun to one of the undercover officers, according to charging papers.

One of the deals with Kim took place in the parking lot of a Pizza Hut restaurant in Federal Way, charging papers claim.

Most of the other alleged drug and gun deals likewise took place in the parking lots of Federal Way destinations: a Wal-Mart, an L.A. Fitness gym, a skate park, a public pool and a park-and-ride lot.

None of the guns was sold on campus, Chief Wilson said.

Brian Kelley, 26, of Federal Way, was the oldest adult charged in the case. Kelley allegedly sold $100 worth of marijuana to the male undercover officer in the Twin Lakes Plaza parking lot. Another student, whom the detective had met during lunch period at Decatur High School, had introduced Kelley to the detective.

The detective asked Kelley if he could also sell him Ecstasy, but Kelley allegedly told the detective "he wasn't into that anymore because he had a baby."

Police anticipate additional arrests.

Diane Turner, a spokeswoman for the school district, said it's uncommon to put undercover officers, posing as students, inside the schools. She said the district weighed recent shootings and "an increased use of drugs and alcohol use among kids" before allowing police to go ahead.

"The decision, given the activity in the community, wasn't difficult," Turner said. "The commitment is safe schools."

In 2003, three Redmond High School students were charged with selling cocaine, marijuana and OxyContin to an undercover police officer who posed as a student.

Police said the undercover investigation in Federal Way is not related to an incident last month in which a 15-year-old boy was charged with trying to sell stolen guns at Beamer High. Two other boys, one the 15-year-old son of a State Patrol trooper, have been charged as juveniles with six counts of weapons theft in Pierce County in an alleged plot to steal the guns from the trooper's Puyallup-area home and then sell them, according to the Pierce County Prosecuting Attorney's Office. The third boy, 16, allegedly stashed three of the guns in a trash bin.

David Bowermaster: 206-464-2724 or dbowermaster@seattletimes.com.

Information from Seattle Times staff reporter Jennifer Sullivan is included in this report.