The explosion happened shortly after seven at an East Bay MUD utility substation near Geary Road and Putnam Boulevard. Walnut Creek police issued a community alert at 7:52 a.m. to let residents know that a fire had shut down Geary Road between Buena Vista Avenue and Hall Lane.
Several dozen utility customers may be affected by service outages.
Firefighters are still at the scene where the blaze is still smoldering. There is no word yet on the cause, of if there are any injuries.