The blast occurred near Esparto and Madison, sending thick black smoke into the air and igniting fireworks that triggered spot fires across the area.
The warehouse building collapsed, but no injuries were reported.
Authorities have urged residents to avoid the area for several days while firefighters work to contain the blaze, which had burned around 32 hectares by Tuesday night.
Explosives experts will have to wait for the site to cool before beginning an assessment.
The cause of the incident remains under investigation.
