Seven women and three children have been found dead at a police station after being arrested on two other charges.
The bodies of seven women and three children were found at a former police station in El Salvador.
Hugo Osorio Chavez Osorio, 51, is being investigated for sexual offenses and killing 13 people, the attorney general’s office said.
He was initially arrested last Saturday for the murder of a mother and her eldest daughter, which he admitted, according to The Associated Press.
The arrests came as neighbors in the western city of Chalchuapa called police and told them they had heard a mother asking for help.
Authorities found the bodies of a 57-year-old woman and their 26-year-old daughter in the house with a pool of blood with signs of torture.
The search led to excavations at various sites in the area. Among the bodies found were a 7-year-old girl and two boys between the ages of 2 and 9.
Police did not say why 13 of the killings being investigated.
Some of the men appeared to have been killed about two years ago, the attorney general’s office said on Twitter.
Seven other potential tombs in the area are still being investigated. At least 25 people are known to be missing in the area.
Chavez Osorio was fired from his job as a police officer in 2005 for adultery and spent five years in prison, investigators said.
According to the affidavit, the jury granted arrest warrants for nine other people who may have assisted in the killing of 13 women, including the murder of eight women.