SACRAMENTO — The state Assembly passed a bill Wednesday sought by San Francisco officials to expand conservatorship rules so they can have more control over who can be involuntarily held for mental-health treatment.

The bill now heads to the state Senate, which has already approved a similar version. If passed there, SB1045 by Sen. Scott Wiener, D-San Francisco, would head to Gov. Jerry Brown.

The bill would allow the Boards of Supervisors in San Francisco, San Diego and Los Angeles counties to create five-year pilot programs that expand conservatorship rules.

“This pilot will provide for the least restrictive and most clinically appropriate placement including supportive housing and wrap-around services,” said Assemblyman David Chiu, D-San Francisco, before the bill passed the Assembly by a vote of 61-0.

San Francisco Mayor London Breed and Supervisor Rafael Mandelman testified in support of the bill at the state Capitol earlier this year, saying the city needed more power to help chronically homeless people suffering from both mental illness and substance abuse.

County mental health professionals can now hospitalize people against their will for 72 hours, in what is known as a 5150 hold, if they pose a danger to themselves or others or are gravely disabled because of mental illness. A county can ask a judge for a 14-day extension to continue intensive treatment and repeat that process every 30 days.

Supporters of SB1045 say the guidelines for a hold are too strict, resulting in severely mentally ill people with drug and alcohol addiction returning to the streets. Wiener said that even the bill’s expanded criteria would apply to only 1 percent of San Francisco’s homeless population.

“It’s beyond inhumane to sit back and let these people die when we have the ability to help them,” Wiener said in June. “Our current conservatorship laws are inadequate.”

Opponents of bill, including Western Center on Law and Poverty and American Civil Liberties Union, said expanding involuntary holds is an affront to civil rights and ignores the factors that lead people to homelessness in the first place.

Melody Gutierrez is a San Francisco Chronicle staff writer. Email: mgutierrez@sfchronicle.com. Twitter: @MelodyGutierrez