A power outage Monday morning left 5,122 customers without electricity in Alhambra and South Pasadena, a Southern California Edison spokesperson said.

The incident, which began at 8:47 a.m., initially knocked out power to four local schools and several traffic signals in the area, officials said.

As of 9:30 a.m., electricity was restored to William Northrup and Emery Park elementary schools, a spokeswoman for the Alhambra Unified School District said. Marguerita Elementary School and Alhambra High School remained without power.

In a statement, the Alhambra Police Department urged motorists to “use extreme caution approaching intersections where the traffic signals are not functioning.”

The cause of the outage was not immediately known.

The issue was expected to be resolved for most customers by 11 a.m., according to SCE.