PHILADELPHIA — Investigators began excavating the backyard of an Olney home on Tuesday as part of a widening search for evidence connected to seven missing or unidentified women. Crews first removed a shed behind the home, then used an excavator to dig beneath its former location. Soil was placed on a tarp, transferred into buckets and sifted under a tent, while investigators continued moving in and out of the property. The FBI and Philadelphia police have not publicly detailed what they are seeking in the yard. The home was formerly owned by the late Raymond “R.C.” Horsch and his son Eugene. The backyard work follows searches inside the house. Investigators worked late Monday using luminol, a chemical that can reveal traces of blood not visible to the naked eye. Police sources said the test produced a reaction that requires further analysis; the result does not establish what caused it. Last week, investigators also dismantled parts of the home, opening walls and floors and removing items from the basement, including laboratory equipment and containers. Authorities are reviewing more than one million digital files recovered from hard drives. No bodies have been reported found. Eugene Horsch remains in federal custody but has not been charged in connection with the missing or unidentified women. The prolonged search has drawn concern from people following the investigation. Tara Gallucci, who traveled from Scranton, said the scale of the work was difficult to witness and emphasized that the investigation involves people with families and loved ones.