SAN SALVADOR, Oct 7 (Reuters) - The skeletons of 12 people in El Salvador, found inside a clandestine grave site at the home of a former police officer, were returned to relatives on Thursday, the latest development in a gruesome case that has shocked the Central American country. The remains of the victims, including two boys and a girl, were handed over to eight families in a private ceremony inside the country"s forensic institute of legal medicine in capital San Salvador. A Reuters witness said a caravan of vehicles then carried the remains to different locations. Graciela Sagastume, the coordinating prosecutor for femicide cases, said the remains of potentially 30 people, mostly women, were retrieved from one of 11 graves inside what local media have dubbed the "house of horrors" in Chalchuapa, a small town about 80 kilometers (50 miles) from San Salvador. read more "The investigation is progressing," Sagastume said at a news conference. "[There are] around 30 bodies that could be recovered, but it is an approximation." Salvadoran police arrested former policeman Hugo Osorio at his home in early May after neighbors reported hearing a woman screaming as she tried to escape his house. Officials found several bodies including those of his brother, two women and another man. They said many more were buried in makeshift graves on the property. Since then, public officials have provided conflicting accounts of the victims tally, prompting criticism over a lack of transparency in a case that has shaken El Salvador, a country no stranger to violence. Osorio is being held in a maximum security prison, facing charges including a double aggravated femicide, and a potential sentence of up to 100 years in prison, said Sagastume. Ten other people are also facing charges in the case.