Battling the four-alarm fire eventually involved 50 firefighters, according to the Los Angeles Times. Local fire department spokesman Captain Antonio Negrete called the damage "heartbreaking."
"The roof of the mission is completely gone and the interior up to the altar is completely destroyed," Negrete said, noting that it was not yet possible to establish the cause of the fire because of concerns over the building's structural integrity.
"We're going to have building engineers come in and see if we can shore up some walls to make it as safe as possible for the investigators to go in and start investigating this fire," he said, according to the Times.
Adrian Marquez Alarcon, spokeswoman for the Archdiocese of Los Angeles, said that because of renovations underway at the church ahead of its 250th anniversary, historic paintings and artifacts had been removed and were not in the building at the time of the fire.
Los Angeles Archbishop Jose Gomez visited the church Saturday morning, saying on Facebook that "[he] woke up before dawn this morning to news that our beloved San Gabriel Mission, founded by St. Junípero Serra in 1771, was burning."
"Thank God no one is hurt," Gomez said. "I'm here to pray with the people. The roof is destroyed and there is much damage in the old church. St. Junípero, pray for this city, this state, and this country that you helped to found."