OAKLAND — Alameda County District Attorney Nancy O’Malley on Tuesday announced that her office plans to dismiss thousands of old marijuana cases now that recreational use is legal in California.

Proposition 64 legalized possession and recreational use of marijuana for people 21 and older and allows for anyone convicted of a marijuana crime to petition to have the convictions reduced or expunged.

O’Malley said the DA’s office has so far identified about 5,900 cases that are eligible for dismissal.

“California is offering a second chance to people convicted of cannabis crimes, from felonies to small infractions, with the opportunity to have their criminal records cleared,” O’Malley said in a statement. “We join our state officials and intend to reverse decades of cannabis convictions that can be a barrier for people to gain meaningful employment.”

Last month, San Franciso District Attorney George Gascon announced a similar plan and said his office will review and recall up to 4,940 felony and 3,038 misdemeanor convictions. Because so few people have filed petitions — 23 over the past year — Gascon said people convicted of cannabis-related crimes will not need to file a petition.

In Santa Clara County, the District Attorney’s Office will review petitioned cases presented by the Public Defender’s Office for potential expungement.

Alameda County officials said 609 petitions were filed and granted from November 2017, when Prop 64 passed, to Dec. 31. Unlike San Francisco, Alameda County prosecutors will conduct background checks, meet with the petitioner, and both sides will come to an agreement before signing and submitting the petition. Officials expect to receive up to 100 cases per week, dating as far back as 1974.

Oakland Councilmember Rebecca Kaplan called the announcement “a step in the right direction.” Kaplan wrote a letter to O’Malley last week asking her to consider a proactive process of expunging cannabis records and said enforcement of marijuana laws has disproportionately affected African Americans.

“I don’t think it’s the end of what we need to do,” Kaplan said Tuesday. “Fundamentally, I think it’s incredibly unjust for anyone to keep being punished for activity that is no longer a crime.”

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Anyone who thinks they are eligible to have their case reviewed is asked to contact the DA’s office at CannabisDismissal@acgov.org.

Staff writer Robert Salonga contributed to this report.