A replacement nurse at an Oakland hospital committed a "medical error" while administering a dosage of medication to a cancer patient leading to her death early Saturday morning, police and hospital officials said.

The name of the woman, a 66-year-old Oakland resident who had been a patient at the Summit campus in Oakland since July, was not released.

An autopsy is scheduled for Monday, but the woman's death is believed to have been caused when an Alta Bates Summit Medical Center replacement nurse "administered a nonprescribed dosage of medication," said Oakland police Sgt. Mike Gantt. Police would not say what type of medication it was and how much was given.

The medication was administered, and a few hours later the patient was found unresponsive during rounds, and she died a half hour later at 1:03 a.m., Gantt said.

The nurse, who came to the hospital from another state to work during the recent one-day nurses strike, was questioned and released by Oakland police. In the interview, the nurse said she made a mistake, but police are still trying to determine whether it was an accident, Gantt said. Her name was not released.

The Alameda County District Attorney's Office was notified and will review the case Monday.

Multiple investigations are under way, and in a statement released Saturday the hospital confirmed the death was caused by a "medical error" but did not elaborate, citing privacy laws. The hospital confirmed it was a replacement nurse.

The hospital said the woman died after "doctors and clinical staff were unable to revive the patient." After the woman's death, the hospital contacted the Alameda County Coroner's Office, which contacted Oakland police.

"This is a tragic event, and our heart goes out to the family of the patient," said Carol Weis, chief nursing executive at the Summit campus.

"We have met and spoken with the family of the patient to express our sorrow and sympathy and let them know our prayers are with them," she said.

The hospital said it is conducting an investigation into the death and is also working with local, state and federal agencies that are also probing the death.

The death "likely was caused by a medical error," said Dr. Steve O'Brien, an Oakland campus medical executive, adding that the hospital activated its patient safety analysis process to review its policies and procedures for opportunities to improve its patient care.

"While medical errors do exist in healthcare we are constantly investing in ways to improve patient care," the medical affairs vice president said in a statement. "This is a most unfortunate event for which we are very sorry."

Nurses throughout Northern and Central California went on strike Thursday, and most non-Kaiser nurses have been locked out for five days. The lockout affects at least eight hospitals run by Sutter Health, including the Oakland hospital.

"We said from the outset that the lockout by Sutter was unnecessary, reckless and unwarranted," said Chuck Idelson, a California Nurses Association spokesman.

"Now we have a very serious concern about the replacement nurses that they have employed during the unwarranted lockout."

The nurses union called the state Public Health Department on Friday, before the incident, Idelson said, to ask for an investigation into demonstrated clinical competence and proper certification of the replacement nurses.

"On Friday, we heard anecdotally about serious concerns about actions by replacement nurses at the two large Alta Bates campuses," Idelson said.

At least one oncology nurse at Summit tried to report for work Friday, but was turned away, he said.

Sutter officials have said they entered into contracts with replacement nurses that require a minimum number of days.

"Once a strike is called, it would be financially irresponsible for hospitals to pay double to compensate both permanent staff and replacement workers," Sutter Health said in a statement earlier in the week.

Nurses, who do not get paid during lockouts, warned Sutter two weeks in advance of the strike, and other companies, like Kaiser, have not locked out their striking nurses, Idelson said.

The Sutter lockout is scheduled to end Tuesday.