WHEAT RIDGE, Colo. -- Recent arrests for heroin at Cheyenne Mountain High School highlight a national trend happening among teens, drug experts said.

More and more high schoolers are turning to heroin -- and not marijuana or cocaine -- as their drug of choice. The teens first get hooked by taking pharmaceuticals.

A legal painkiller called Oxycontin is quickly becoming a gateway drug to heroin.

"People don't realize how that drug is formulated. If you cut into Oxycontin, you crush it up, what you're left with is a phenomenally pure, phenomenaly strong ... really a heroin that comes in a pill bottle," said Jeff Sweetin, special agent in charge of operations at the Drug Enforcement Agency in Denver.

"Jaffar," a 17-year-old former student at Cheyenne Mountain high school in Colorado Springs, said he thought that smoking a substance he didn't create himself was just a good way to get high.

"I was under the assumption, just like everyone, that it was opium we were smoking," Jaffar said. "If we would've known that it would've been heroin, I think most of us wouldn't have picked it up the first time."

Jaffar said before smoking heroin he started taking perfectly legal prescription painkillers, such as Oxycontin, with no clue that it was getting his body adjusted to opium.

Because he and his group of friends -- at least 20 strong he says -- weren't injecting anything, they thought they were safe.

"And, you know, everyone thinks it's becoming OK now," Jaffar said. "Twenty dollars got you high for the day, basically."

Colorado Springs police have now made five arrests in the heroin case, which began in October. Some were students. The arrests were made very close to large mansions and the Broadmoor Hotel.

Sweetin said his agents are seeing an attitude change towards drugs, with many believing they're not really dangerous and that government warnings have been lies.

Lately, it's become harder, Sweetin says, to get meth and cocaine on the streets. That's not true though of another incredibly addicting and powerful drug.

"Heroin is still readily available on the street in Denver, Colorado," Sweetin said.

It's a cycle one drug treatment professional specializing in teens clients has seen repeated every eight to 10 years since the 1960s, with one big difference.

"Yeah it's stronger now than it was 30 years ago, no question," said Dr. Alex Panio with the Adolescent and Family Institute of Colorado.

Jaffar is no different from the other half-dozen teenagers he's seen for heroin addiction in the past four to five months; they all believed smoking was a better alternative.

"The illusion is that this is safer, cleaner, is an illusion. And by definition, it's a myth," Panio said.

Pharmacies are also seeing the effects.

The Wheat Ridge Professional Pharmacy has been broken into five times since April and has now cut back on the amount of Oxycontin they carry.

The DEA has added staffers for first time in years to attack the diversion of prescription drugs, like Oxycontin, onto the black market.

The experts say these are telltale signs parents can watch for:

Tin foil crumpled up with burn marks, possibly in a car or bedroom.
Lighters.
Pens that have been hollowed out.
Weight loss. Heroin users tend to crave less nutritious foods like sweets and fast food.
Large amounts of money missing.
Prescription medications missing or greatly reduced.