Investigators are slowly clearing rubble from the second chamber in the bricked-up cellar.
So far, there are no reports of blood or bones being recovered in the chamber, which is three times the size of the 12-foot square chamber found over a week ago. The chambers are allegedly part of a network of punishment rooms. Police believe there are two additional rooms.
Police have said a murder inquiry could now be launched as the result of the investigation of child abuse at Haute de la Garenne.
The Telegraph reports: Lenny Harper, the island's deputy chief police, was speaking after giving details of the disappearance of a young girl from the Haut de la Garenne home in the 1970s. She apparently vanished after being subjected to an "act of violence" there, Mr. Harper said.
It is the first time police have referred to the disappearance of a specific individual from the former home in St Martin. Mr. Harper said: "Of course we cannot rule the possibility out that this could be a murder inquiry.
"That is one of the reasons we are carrying out the operation at Haut de Le Garenne.
"As we have stated previously, we have to treat the scene as a major crime scene and possible homicide until proven otherwise."
The force has so far not named the potential victim.
Mr. Harper gave details of the girl's disappearance, based on an eye-witness account.
He said the girl could have been killed in what he described as "an indirect act of violence".
He continued: "The witness claims that the child was not seen or heard from again after the incident."
However, Mr. Harper also added: "There could have been an innocent explanation for her disappearance from the home.
It is hard for me to believe that with all the witnesses coming forth with tales of rapes, beatings and abuse that there hasn’t been a purposeful and systematic cover-up, here. There is just too much corroboration.
Senator Stuart Syvret Blog