SAN DIEGO — Power has been partially restored to Richard J. Donovan Correctional Facility after one of the facility’s main transformers malfunctioned nearly three days ago, leaving inmates without working lights or toilets.

The outage began Wednesday morning around 8:35 a.m., leaving the 780-acre prison without electricity, air conditioning and running water. Large generators and portable toilets were brought in to help with some operations.

According to the CDCR, San Diego Gas & Electric crews determined the loss of power was caused by damage to one of the primary transformers that supplies power to the majority of the facility.

Officials with the California Department of Corrections and Rehabilitation told FOX 5 in a statement that all housing units and clinics resumed full power through generators around 7 p.m. on Friday. All toilets and electronic tablets given to inmates are also up and working again.

“(RJD) continues its progress toward resuming normal operations,” CDCR spokesperson Terri Hardy said in the statement. “Electrical crews will work throughout the night to continue to bring full power to additional areas.”

FOX 5 learned of the outage on Thursday after receiving reports from concerned family members who were worried that the basic needs of their incarcerated loved ones were not being met.

In addition to lights, families said that the loss of power has impacted the availability of clean water at RJD, as well as the flow of air throughout the facility.

“No fresh air, no running water — they have a porta potty that I’ve heard that 200 have to share and they’re being escorted one at a time,” one inmate’s fiancé, Janice Oliver, said to FOX 5 Friday afternoon.

According to CDCR, large-scale generators and portable toilets were brought in as crews worked to address the issue. Normal food operations were also paused and cold meals are being served to inmates.

“The health and safety of all who live and work within our institutions and in our communities is our top priority,” Hardy said in a statement on Thursday. “The outage does not jeopardize security at RJD, and health and impacts are being addressed in a timely manner.”

Families who spoke with FOX 5 before power to the clinic was returned through the generators said that one of their biggest worries was for those inmates with medical conditions.

“We have a lot here that are sick that use the CPAP machine, that get dialysis. My husband has stage four cirrhosis and he’s also a heart patient, so that is a big concern for me as well,” said Mary Estrada, wife of an inmate.

Families say visits for most inmates were also canceled for this weekend.

A timeline for when power might be fully restored to the facility has not been determined. RJD said SDG&E and the facility’s high-voltage contractor are still working to evaluate the damage.

In a statement, SDG&E said crews were “actively investigating” the cause of the outage and were working closely with CDCR to address the issue as quickly as possible.

“SDG&E’s electric system is energized up to the electric system of the correctional facility, but before power can be restored, customer-owned electrical equipment must first be repaired. Our crews were onsite yesterday and are onsite again today,” the statement continued. “We stand ready with personnel and parts to rewire our equipment once the facility’s equipment is repaired.”

FOX 5’s Jason Sloss contributed to this report.