Los Angeles detectives assigned to the Grim Sleeper serial killer case say they are investigating  two additional homicides that may be the work of suspect Lonnie Franklin Jr., according to an aide for an L.A. councilman in whose district some of the killings took place.

The detectives also said there are four missing persons cases that may be related to the overall investigation, the aide told CNN.com Thursday.

In July, 57-year-old Lonnie David Franklin Jr. was arrested and charged with 10 murders and one attempted murder related to slayings that date to 1985. He has pleaded not guilty. In 2009, CNN.com published a special cold case interactive on the decades-long hunt for the killer. Police were led to Franklin after his 28-year-old son was arrested and gave a DNA swab, authorities said. When authorities announced the arrest, they revealed that Franklin had, for a time, worked as a garage attendant at a Los Angeles police station.

Who is Franklin?

Detectives delivered the news about the additional cases at a community meeting Wednesday night at Bethel AME Church in South Los Angeles. They were responding to a question from a family member of one of the two homicide victims, according to the Los Angeles Times.

Dennis Gleason, a spokesman for Eighth District Councilman Bernard Parks, told CNN that the possible additional homicide victims were identified through photographs related to the Grim Sleeper case that police released to the public in December.

Shortly after Franklin's arrest, police searched his home and said they found Polaroids and videotape of many women. In December, investigators released some of those photographs (viewable here), which generated leads, they said.

Franklin is in custody awaiting trial.