K-9s to search "house of horrors" in Philadelphia for clues in Horsch investigation, sources say

Police and the FBI are almost finished removing items from the Horsch residence in the Olney neighborhood of Philadelphia as the investigation into the so-called "house of horrors" continues to expand.

Investigators have recovered valuable items for the investigation while searching the house at 417 West Chew Ave. every day this week, sources say.

They plan to take more pictures Friday inside the home and bring in K-9s to sweep the property that was home to the late Raymond "R.C." Horsch, a suspected serial killer whom sources say preyed on vulnerable women in Kensington.

Cache, the Philadelphia Police Department's electronic-sniffing dog, will work with the investigators Friday, sources said.

The dog is trained to detect hidden thumb drives and file-storing data drives and cards and can smell oils on those devices, even when they're hidden.

What comes next in Olney investigation

Detectives expect to use luminol Monday to look for blood in the house. They'll do that after dusk when sources say any results will be easier to see.

Investigators will bring in heavy equipment Tuesday to dig up parts of the property in an effort to find any trace of several missing women connected to the property. 

Investigators are looking for evidence to corroborate what they have seen on some of the 1 million images and videos recovered from the residence, including files that show women who appear to be unconscious.

Police have not recovered any human remains.

Pipes were clogged, sources say 

Investigators removed sewer pipes from the property in July and sent them for testing. Both of the pipes connecting the house to the city sewer system were clogged, and one was out of service, sources told CBS News Philadelphia this week.

Forensic teams entered the home's basement Tuesday and began dismantling a laboratory. A source close to the investigation told CBS News Philadelphia the basement was broken into a number of rooms and resembled an old high school science lab.