The Morgan Fire, which was initially reported around 1 p.m. Sunday off of Morgan Territory Road near the park and southeast of Clayton, was fully contained at 3,111 acres as of 5:30 p.m. Saturday, Cal Fire officials said.
Winds and dry vegetation helped fuel the fire, which prompted the evacuation of some 75 homes. Residents were allowed to return to their homes by Tuesday, according to fire officials.
Cal Fire will be handing command of the fire back over to local fire agencies today and resources are being demobilized, but firefighters will continue working to mop up inside the fire containment lines, according to Cal Fire.
Around 231 firefighting personnel remain on the scene, Cal Fire officials said.
Fire investigators have determined that target shooting in the area on Sunday caused the Morgan Fire.
In a statement released by Cal Fire, fire officials urged people living or visiting California to "be extra cautious with any activity that may cause a spark."
Mount Diablo State Park is on track to partially reopen on Monday, and crews are working to fix park trails and structures damaged in the blaze, according to park officials.