The child's body has not been identified but it may be Ethan's, sheriff's Lt. Glenn Giannantonio said late Tuesday.
Christina Anderson's father, Christopher Saincome, said Wednesday that his daughter visited DiMaggio's home last weekend to say goodbye before he moved to Texas. DiMaggio, who works as a telecommunications technician at The Scripps Research Institute in San Diego, was a regular presence at the Anderson family apartment in Lakeside, a suburb of 54,000 people.
"He must have had this planned," Saincome said.
Saincome said nothing seemed amiss when he called his daughter at work Friday to let her know she didn't call on his birthday. Anderson, a medical assistant, said she would call back that night but never did.
Investigators had no evidence that the relationship between DiMaggio and the missing girl was more than friendly.
"We're not looking into that directly at this point," Giannantonio said.
DiMaggio is wanted on suspicion of murder and arson in the search that began in Southern California and spread to Mexico and neighboring states.
DiMaggio's sister, Lora Robinson, told U-T San Diego that the allegations against her brother were "completely out of character." She said he spent four years in the Navy, left military service to care for her after their mother died of cancer and volunteered rescuing animals.
"He is the kindest person in the world," Robinson said.
She told ABC's "Good Morning America" that she believed her brother was also a victim of foul play, along with the Andersons.
"He tried to take care of those kids, and he took care of them as if they were his own," Robinson said.