Philadelphia police and FBI investigators planned to search a home at 417 W. Chew Ave. in Olney for possible traces of blood after nightfall Monday, Oct. 12, using the chemical luminol. Excavation equipment was expected at the property Tuesday to dig into portions of the backyard as the investigation continued. The home belonged to Raymond “R.C.” Horsch, who is dead. Investigators have returned to the residence over several months, looking for evidence of foul play and possible human remains. Police sources have said evidence collected there could help investigators determine what happened to as many as seven missing women connected to the property and Horsch. Luminol is used to detect possible blood traces. Retired FBI supervisor Richard Marx said the chemical can produce a faint blue glow when sprayed on material believed to contain blood, making darkness helpful during a search. He cautioned that it is a presumptive test, not confirmation on its own that a substance is blood. Marx said investigators may be able to detect old traces because blood can soak into porous materials, including carpeting and gaps in hardwood floors. Horsch’s son, Eugene Horsch, remains in custody on drug and weapons charges while awaiting a federal trial. His attorney has declined to comment on the case or whether Horsch has spoken with investigators. The planned chemical testing and backyard excavation are part of an ongoing effort to establish whether crimes occurred at the Olney residence. Investigators have not publicly confirmed that blood or human remains have been found there.