"We have confirmed one arrest in the case, but are not releasing any other details," AG spokeswoman Christine Gasparac tells PEOPLE. She adds that the probe into the crime ring began long before Haim died and that the suspect may not have directly supplied the drugs that caused his death.
Haim obtained "thousands of pills" from multiple doctors going back to 2009 that he "shopped to," Attorney General Edmund G. Brown Jr. told CNN's sister network HLN.
"How many people go to 10, 15 or 20 doctors and then run around to 10, 12 and more pharmacies to go fulfill them? And sometimes two different doctors on the same day?" Brown asked. "If he took all the pills that our records show he was prescribed over the last year and three months, he took some very damaging assaults on his body."
Brown's office previously confirmed that a fraudulent prescription for OxyContin in Haim's name was discovered during the investigation: "We know there was a [doctor's] pad stolen and there was a prescription written for him using that pad, so it was fraudulent and we know it was filled," Gasparac said.
Brown told HLN that Haim's OxyContin prescription was from last year.
The L.A. coroner confirmed that four prescription pill bottles – which reportedly included Vicodin and Valium – were found in the actor's name at his mother's apartment where he collapsed on March 10.
Although police mentioned an overdose as a possible cause of death, the official determination is pending toxicology results.
The actor, 38, was laid to rest Tuesday in Toronto.