FULLERTON (CBSLA) — Power outages hit Fullerton and Valencia, leaving thousands of people in the dark and heat overnight.

SoCal Edison crews have been working throughout the night to bring power back to both communities, which are 60 miles from each other. Fullerton was hardest hit, with as many as 13,900 customers without power at the height of the outage, which was first reported at about 8:40 p.m. Monday.

As of 5 a.m., just 87 customers in Fullerton were still without power. The cause of the Fullerton outage is still under investigation, but SoCal Edison says most of the power should be back up soon.

In Valencia, an outage was first reported just before 7 p.m. Monday, hitting more than 1,400 customers at one point. Power was restored to more than 1,300 customers by 1:20 a.m., and equipment problems were blamed as the cause of the Valencia outage.