LA CROSSE, Wis. -- Police say it's like someone threw a switch.

Two years ago, heroin was a drug they barely saw on the streets of La Crosse. Now, they say heroin use is one of our community's biggest problems.

Investigators say the drug is becoming more and more popular, especially among young people who used to abuse prescription painkillers. Both are opiates -- a highly addictive drug that causes euphoria.

Thanks to new regulations, people who abused painkillers are finding the pills more expensive and harder to get. So, many of them switch to heroin looking for a more extreme high for a lot less money.

These days, Detective Sgt. Dan Kloss goes on a heroin buy once a week.

“We're going to a south side residence, where an informant is going to go inside a residence and purchase heroin and come back out to us," said Kloss.

Two years ago, heroin wasn't even on his radar. That was before dealers realized they could make a killing selling it in La Crosse.

"Exactly. They can go down there [to Chicago], buy it in bulk, come up here, and piece it out, and make -- what I'm told -- triple, four times the profit off what it is in Chicago."

So why are people in La Crosse paying more for heroin? Let's take a look at the numbers. Two hits of heroin costs $30 to $50. Now look at the alternative. One prescription pain pill costs $80. It's a cheaper high for users and higher profit for dealers.

"We have a very high demand for the drugs. And it's very profitable,” said Kloss.

The police department's strategy for stopping the rampant sale of heroin is to go after the dealers. That's where the informants come in.

One informant working for Kloss was caught dealing heroin last summer. Kloss cut this person a deal: they could get a reduced sentence -- maybe even get it eliminated -- if the information helps police catch other dealers.

But this informant claims to be unconvinced police can make a significant dent. Even if dealers know other dealers are getting caught, the money can be hard to resist.

“I mean, you make more than you would in a two weeks' payroll in an hour, not even," said the informant.

Besides the fact that high demand is driving prices up, there's another reason dealers can make more money off heroin in La Crosse.

By the time it gets all the way to a small city like La Crosse, it's passed through a lot of hands. Each time, it's mixed with something cheap like baking soda or baby formula. That way the dealer can sell a weaker product for the same amount of money.

It's pure profit, but the problem is a buyer never knows how pure the heroin is.

"It literally is like playing Russian roulette. You don't know how potent it is, how pure it is. You just don't know. And some users will try that heroin and, depending upon the purity of it, it could be their last time," said Kloss.

There have been seven confirmed heroin deaths in La Crosse County since 2010.

County Medical Examiner John Steers said he's seeing a disturbing trend.

"Most of them are in their mid-20s, you know, people who are experimenting with drugs in their earlier years," said Steers.

"You don't know how many lives you saved by taking down just one dealer. We'll never know. But I guarantee you it's significant,” said Kloss.

Arresting dealers gets them off the street and into the courtroom.

But are our courts doing enough? Police say dealers tell them one of the reasons they come to La Crosse is they think the legal system here is soft.