Investigators in Mexico said Saturday that they have found nearly 4,000 bone fragments, which apparently belonged to 17 different victims, underneath the house where an alleged serial killer lived, ABC News reports

A search of the property began after the 72-year-old man, who cannot be named due to Mexican laws which protect a suspect’s identity, was arrested for the gruesome murder of a 34-year-old woman last month.

The discovery was made because the victim’s husband is a police commander whom the alleged serial killer knew personally. He believed that the suspect, identified by prosecutors as “Andrés,” was responsible for her death since he and his wife planned on going out shopping the same day she disappeared. The police commander was able to view police surveillance camera footage showing his wife entering the street where Andrés lived but never leaving. When he confronted the suspect inside his home, he found her dismembered body. 

Investigators found voter IDs, women’s clothing, and ID cards belonging to people who had been missing for years. A search underneath the concrete floors of the suspect’s home resulted in the discovery of 3,787 bone fragments, which leads them to believe that Andrés, a former butcher, hacked his victims into pieces. 

“The bones fragments are being subjected to ‘lateralization’ studies, which include carefully cleaning each one, identifying what part of the body they are and then placing them in their anatomical position, providing a method for determining the approximate number of victims,” prosecutors said in a statement. “This analysis indicates that, up to now, the bone fragments found may possibly be those of 17 people.”

Nearly 30 8mm videotapes, which were discontinued around 2007, and 25 VHS cassettes were found inside the home, suggesting that these killings could date back over a decade ago.