Emergency crews were called out to Space Launch Complex Two at Vandenberg Airforce Base when a fire broke out on Thursday.
Black smoke was billowing into the sky at a site that was being dismantled by a copmany idenitfied as Firefly Aerospace, which is developing new rokcets to launch from that same location.
Officials at the base says welding equipment was being used at the time.
The fire broke out at about nine in the morning and burned for two hours.
The last time the launch site was used was September 2018.
Delta rockets had taken off from the area carrying military satellites and occasionally scientific and commercial gear.