The U.S. Federal Bureau of Investigation (FBI) is currently running 130 different cryptocurrency-related investigations, Bloomberg reported Wednesday.

FBI Supervisory Special Agent Kyle Armstrong told the Crypto Evolved conference in New York that the agency is investigating a variety of crimes, including human trafficking, drug transactions, kidnapping and ransomware, which have a cryptocurrency component, according to Bloomberg.

Further, there has recently been an uptick in cases involving cryptocurrencies, he said, citing opioids as one area where the bureau needs to focus on. Roughly 10 percent of drug users worldwide purchase drugs online in illegal digital marketplaces.

Some parts of the U.S. have also seen an increase in extortion schemes, where the perpetrators wish to use cryptocurrencies.

That being said, these “threat-tagged” investigations only make up a “small sliver” of the thousands of  cases the agency has, he said.

And unlike crimes involving cash, Armstrong said the blockchain’s immutability makes it easier to track transactions. On the flip side, cryptocurrencies’ anonymity or pseudonymity make it more difficult to properly investigate a crime.