A bomb squad descended on the quiet street of ranch homes in the Orange County city of Costa Mesa after the 52-year-old man died in the Sunday night blast.
About 90 minutes earlier, neighbors reported seeing the man lying on his front lawn but said he refused offers of help and went inside his home.
Police were called about 7:30 p.m. after neighbors heard the explosion, and the man was found dead.
Police suspect he was killed by some sort of homemade explosive, but investigators had not determined whether the blast was suicide or an accident.
At least two other explosive devices were later found at the home, police Sgt. Jerry Hildeman said.
Neighbors from surrounding homes remained evacuated until the house was declared safe, police said.
The FBI, an Orange County Sheriff's Department bomb squad and other agencies responded to the scene.