The Sonoma County sheriff's bomb squad detonated at least two explosive devices at a Petaluma home early Tuesday and Petaluma police arrested one of the occupants.
FBI agents also responded to the Ely Road area subdivision in northeastern Petaluma.
"We're calling more FBI out to take a better look at the suspect's history, based upon items found inside the residence," said Petaluma Lt. Tim Lyons, who declined to describe the items except to say they were illegal.
"They're (FBI) looking at the whole incident, making sure there's nothing else to this," Lyons said.
Petaluma firefighters also joined the investigation, called in to deal with hazardous materials found, including some of the ingredients for explosives, Lyons said.