Police still have not said what led them to search the house in the 700 block of South Palm Avenue, only saying that the man had some link to the property and the people who live there.
Oscar Contreras Escobar, a 29-year-old self-employed truck driver, has not been seen since August. He had finished his deliveries for the day, and someone dropped him off near the intersection of Foothill Boulevard and Mango Avenue in Fontana.
Ontario police believe foul play in their city may be involved in Escobar's disappearance. The house came onto their radar in November, but it was only two days ago that they finally served a search warrant.
Ontario police focused on the porch area of the backyard. Officials say they have found something of "strong evidentiary value" at the dig site, but did not say what specifically was found. When asked if it was human remains, they would only say there was significant pieces of evidence that need to be shipped off to a lab for further testing.
"I've been told by detectives that these items are probably of such great value that they decided to bring out additional coroner personnel to help with the recovery of the items," sad Ontario Police Sgt. Dave McBride.
Detectives describe the process as painstaking, with up to 20 people in the backyard at once, wearing gloves, many of them on their hands and knees, digging. With the help of a tractor, they've torn apart the concrete slab along the porch, digging as deep as six feet underground in some places.
Even though they've already collected what they're calling "trace evidence," detectives say they want to make sure they don't leave anything behind that might help them figure out exactly what happened to Escobar.
"They're in there quite a ways. Who's to say how deep these items that we're looking for are buried, so we don't want to walk away thinking that we might have left something of importance," McBride said.
Investigators will return to the house on Saturday.
Three people who were at the home were interviewed and released. Authorities are not saying what kind of relationship Escobar may have had with the people who lived at the house.