SACRAMENTO  (AP) — Nearly 150 female prisoners have been sterilized over a five-year period without the required approval of a California medical committee, a newspaper reported Sunday.

Dozens of female inmates received tubal ligations that hadn’t been approved and some said they felt coerced to undergo the surgery, although they signed a written consent. Ten women claim they were sterilized improperly in other procedures, including having their ovaries removed, the Los Angeles Times reports.

“Pressuring a vulnerable population — including at least one documented instance of a patient under sedation — to undergo these extreme procedures erodes the ban on eugenics,” the California Legislative Women’s Caucus wrote in a letter to the federal receiver in charge of prison healthcare.

The unauthorized sterilization involved inmates from the California Institution for Women in Corona and Valley State Prison in Chowchilla.

The operations were done at outside hospitals and medical facilities by doctors under contract with the state’s Corrections Department. Medical directors at the prisons recommended and approved the tubal ligations, Joyce Hayhoe, a spokeswoman for the receiver, said.

“Our physicians were not following the proper procedures,” she said.

Daun Martin, a psychologist who was the medical administrator at Chowchilla from 2005 to 2007, said none of the tubal ligations done at the prison were improper or done under coercion.

“The women who had tubal ligations all signed consents. There was absolutely no harassment or pressure,” Martin said.

A group of lawmakers has asked the California Medical Board to investigate the physicians involved in unapproved sterilizations to determine whether any disciplinary actions or license revocations were warranted, the Times reported.

New procedures to limit sterilizations were implemented in 2010. There has been only one such surgery over the past three years and it was ruled medically necessary. Corrections officials found no evidence of sterilization performed on male prisoners and they have informed all prison medical directors and contract physicians about the restrictions on sterilizations and the need for prior consent.

The allegations were first reported by the Center of Investigative Reporting.