Pharmaceutical drug heists in the U.S. are an ever-growing problem, with thieves stealing large amounts of prescription drugs for resale on the black market, according to a recent Associated Press (AP) report.

The latest heist was at a pharmaceutical warehouse in Connecticut where $75 million worth of drugs were stolen. This type of crime has quadrupled in the past 4 years. Experts warn that scarce security and high drug prices add to the fire, giving thieves a reason to continue with the lucrative crime.

The theft from the Eli Lilly & Co. warehouse on Sunday morning is the largest drug heist on record and confirms that those involved are highly sophisticated to be able to pull off such crimes.

Authorities say the thieves cut a hole in the roof, lowered themselves in on ropes, disabled the alarms, and made off with enough drugs to fill a semi. Top-selling antidepressants Prozac and Cymbalta were among the drugs taken.

“The people that target the pharmaceutical industry are an organized criminal element,” Charles Forsaith, director of supply chain security for drug-maker Purdue Pharma, told AP. “This is not just a couple of thugs who randomly decide to hit a major warehouse,” he added.

Forsaith is at the forefront of a coalition which includes drug companies, distributors and law enforcement agencies who have been working to prevent such crimes since 2006. Since then, however, reported thefts have climbed from 11 to 46, according to security firm FreightWatch International.

Thieves most often hit cargo trucks or cargo containers, but also hit warehouses occasionally. Nearly $97 million dollars worth of drugs were stolen in 2008, and $184 million in 2009. This latest heist was $75 million alone.

Drugs are often sold illegally overseas, but most show up on pharmacy shelves in the U.S. with fake labels and lot numbers. Drugs like morphine and codeine are usually sold on the street.

Many times, the drugs that are stolen and sold back to pharmaceuticals and drug stores, but major drugstore chains say they only purchase drugs from manufacturers or wholesalers that can certify the source of the product. But experts say stolen drugs can be easily resold.

“Some of these thieves completely redo labels, and they pass muster if no one’s looking too closely,” said Food and Drug Administration spokesman Tom Gasparoli to AP.

The resold drugs can be a danger to the public if thieves hold on to the product for too long and it expires and becomes unsafe. But also, “if they flood the market with this stuff now they’re going to get caught,” said Steve Brozak, president of WBB Securities, an investment firm focused on the drug industry.

A year ago, a refrigerated truck carrying insulin was hit by thieves, who got away with almost $11 million worth of the product. Months later the FDA reported many cases of diabetics showing up in ER’s with unsafe blood sugar levels; the cases were traced to the stolen insulin, which was not properly stored.

Pharmaceutical theft is mostly a U.S. problem. In Europe theft is virtually nonexistent because government control keeps drug prices low and most people have good health care coverage, according to Ron Greene, a spokesman for FreightWatch.

In the U.S., where health care and prescription drugs are expensive, “you’re going to have a means to profit from stolen drugs,” said Greene.

Drug makers are taking measures to protect their products. FreightWatch advises companies to hire more security and install tracking systems to monitor where their trucks are at all times.

The Food and Drug Administration is also stepping up efforts to keep the public informed. They are working with manufacturers, distributors, pharmacies and law enforcement, and also posting information on stolen drugs on their Web site.