The Drug Enforcement Administration (DEA) crackdown on improper sales of prescription painkillers, which has been focused on CVS, has now spread to Walgreens, according to The Wall Street Journal.

This week drug agents searched six Walgreens stores and a distribution center in Florida, the newspaper reports. Earlier this year, the DEA ordered two CVS pharmacies in Florida to stop selling controlled drugs. The agency was concerned CVS had failed to closely monitor sales of oxycodone.

The DEA has tried to tighten control on major national pharmacies to help prevent painkillers such as oxycodone from getting on the black market. The agency is investigating whether Walgreens allowed suspiciously large sales of prescription opioids, which might indicate the pills are being diverted.

DEA agents are searching through business records looking for what percentage of customers pay for oxycodone for cash. A high percentage could indicate drugs are being diverted to the black market.

While Florida was long known for its “pill mills,” storefront clinics where customers could pay cash for prescription painkillers, many have been closed after a state crackdown. Demand for painkillers has now shifted to retail pharmacies, the article notes.