Norma Hernandez told ABC News that she went go to Camden police at some point to tell them of her brother's admission.
She also told The Star-Ledger that she did not have details about the killing but went to police about it in the 1980s. She says they did nothing at the time.
"This is the first we are learning of Ms. Hernandez's comments. Since this is an on-going homicide investigation, anything we do will be closely coordinated through the direction of the Camden County Prosecutor, Manhattan DA, and the NYPD," Camden Police Chief Scott Thomson said.
Norma Hernandez previously told The Associated Press that she would have turned her brother in if she'd had more information.
Hernandez has told police that he tossed out Etan's body with the trash near the SoHo bodega where the boy was killed in 1979.
The sanitation department is going through its records to see whether the trash could have been cleared by the city or a private hauler. The collection could have gone to the Fresh Kills landfill in Staten Island, but it could also have been incinerated or tossed in the ocean, which was a common practice at that time.
Get Eyewitness News Delivered