Earlier this week, crews dug up the body of the 53-year-old homeowner, James Stein, in the backyard of a home on the 4800 block of 112th Street. He and his wife Gabriela vanished in December.
Authorities first got word there may be bodies buried in the backyard on Monday. The tip came from the ex-girlfriend of the prime suspect, Marcos Lomeli.
L.A. County Sheriff's investigators arrested Lomeli on Wednesday at a motel in Pico Rivera near Beverly and Rosemead boulevards. Lomeli also lived in the Lennox house.
Hours after Lomeli's arrest, the Lennox house caught fire. The blaze was under investigation by an arson unit.
Anyone with information about this case was urged to call Crime Stoppers at (800) 222-TIPS.
The Associated Press contributed to this report.