MIAMI — If you know where the drugs are coming from, you can stop them at the source.

Or so hope researchers from Florida International University’s International Forensic Research Institute who zeroed in on a component of heroin that could pinpoint where it was grown.

The chemical structure of the drug provides clues to the manufacturing process used to turn opium poppies to heroin, an opioid that killed nearly 13,000 users in the United States in 2015, according to the U.S. Department of Health and Human Services. The problem in identifying the location has been that as manufacturers from different regions processed the drug in the same fashion, pinpointing its source has proven difficult.

Four territories identified by the Drug Enforcement Agency produce the bulk of heroin: Mexico, South America, Southeast Asia and Southwest Asia. The thinking is that if the DEA can determine where heroin entering the United States is manufactured, they can react more quickly and target domestic and foreign law enforcement.

Researchers hoped to find something unique in the heroin itself that couldn’t be masked or eliminated, a component, they figured, the drug makers would overlook. The research focused on the ratio of radiogenic strontium isotopes, which are naturally occurring in bedrock and can be found in different ratios among geographic regions depending on the nature of geologic formation.

“We developed robust analytical methods to measure trace elements in the heroin powder at very low levels as well as measure strontium ratios with the help of our colleague at the University of Miami,” Forensic Research Institute director Jose Almirall, the principal investigator of the study, said in a release. “We demonstrated, for the first time, that strontium can be used as a chemical marker for geography and geology to differentiate heroin samples from different geographic regions.”

The DEA had provided researchers with heroin samples of the four known and distinct geographic regions.

“It’s helpful for them to develop intelligence from heroin that is seized,” said Joshua DeBord, an FIU student who co-authored a recent study validating the effectiveness of this new method.