SAN JOSE — Last July 1 was a normal day at a collectible card store in Newark, until 1,000 drug-filled pills showed up in the mail.

Curiously, packages containing hundreds of pills — some Xanax, others laced with methamphetamine and MDMA — were labeled “return to sender” and had the business’ return address on them. The owner, who knew nothing about the packages and hadn’t sent them, called law enforcement, according to court records.

Now, three South Bay men: John Abidog, Viet Pham, and John Nguyen, are facing federal charges alleging they schemed to transport controlled substances to Massachusetts by mailing packages labeled with return address for various trading card stores around the Bay Area. The charges were filed in Massachusetts but last week the group raided suspected drug ring “stash houses” in San Jose and Sunnyvale, seizing tens of thousands of pills, a “brick” of cocaine, and three guns, according to court filings.

According to the criminal complaint, police in Massachusetts were investigating a suspected drug dealer there and determined he was being supplied from the San Jose area.

The investigation led Post Office investigators to a suspected “stash house” on Pecan Court in San Jose, where authorities installed a secret camera. Investigators also reportedly reviewed footage from post offices were the drugs were shipped and installed a GPS tracking device on Pham’s car, the complaint says. Government surveillance indicated the group was active; on July 23 alone, authorities allege Pham sent “at least 60 packages” using hobby shops or trading card companies.

Authorities also seized various packages with drugs, including ketamine, during the investigation. One person who received 500 Adderall pills and 50 MDMA pills confessed during a police interview to ordering the drugs off the dark web, the criminal complaint says.