The hospital, which housed 200 patients at the time, lost power. The lights briefly went back on after the backup generator kicked in, but the facility fell into darkness again when the emergency generator failed.
"All of our systems failed," hospital spokeswoman Carla Nino said. "Staff stepped up and did a miraculous job. There was no compromise to our patients."
During the 3 1/2-hour outage, nurses tried to calm scared patients, security guards patrolled the pitch-black halls with flashlights and emergency room staffers used hand-cranked ventilators to keep critical patients breathing.
About two dozen patients on ventilators, including 10 newborns, were transferred by ambulance to neighboring hospitals. The hospital did not suffer damage and did not evacuate.
Olive View and the Los Angeles County Department of Public Works are leading the investigation into the generator failure. The hospital also plans to hire a consultant to conduct an independent probe.
At the fire command center over the weekend, Gov. Arnold Schwarzenegger raised concerns about Olive View outage.
"We need to make sure we have good backup generators at our local hospitals," he said.