Enlarge / Attorney General Jeff Sessions talks about the opioid epidemic at The Columbus Police Academy on August 2, 2017 in Columbus, Ohio. (credit: Maddie McGarvey/Getty Images)

Federal authorities announced Wednesday that in recent months, they have arrested, charged, and received guilty pleas from suspects in numerous new drug cases stemming from dark Web sites. Prosecutors collectively dubbed this project “Operation Darkness Falls.”

The most prominent of these cases involves Matthew Roberts and Holly Roberts, a possibly married couple from San Antonio, Texas that jointly operated under the name “MH4Life.”

According to federal prosecutors, the two suspects were “the most prolific dark net fentanyl vendor in the United States and the fourth most prolific in the world” at the time of their April 2018 arrest.