The Fresno Unified School District said a transformer went out and teams worked through the night to fix the problem.
PG&E says it was notified about the issue early Monday morning.
"We went out and did an initial inspection. We're able to work with the high school to identify what exactly the problem was and what needed to be done to fix it," said Jeff Smith with PG&E.
PG&E says the issue is on the school's end.
The district says they have hired an electrician to fix the problem.
"We've been in regular communication with them yesterday and today," Smith said.
"We have folks on site today that are waiting for the electrician that Sunnyside High School is working with to complete their work and once that is complete, pg&e will be able to get the power restored."
The district did not tell action news when the electrician's work would be complete.
"Our portion should really be able to be completed relatively quickly once the work is done on the customer side," Smith said.
In the meantime, other Fresno Unified schools, including CART, remain in session.
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