Forensic scientists are excavating two pits at a former home in Jersey at the centre of a child abuse inquiry, police said today.
A member of the public came forward saying he had been asked to dig and fill in the pits near the boys' dormitory by care staff before the school was closed.
About 160 people have said they were abused at Haut de la Garenne, which closed as a children's home in 1986.
A large amount of lime was found in the first pit, which was about 1.5 metres deep. Work is still being carried out on the second.
"The inquiry team can think of no reason why this pit would have been created nor why it was filled with lime," said a police spokeswoman. "We would emphasise that we have no evidence of any motive."
The holes, at the back of the building, were dug in the late seventies or eighties.
"According to the witness, this has played on his mind for some years and led to him coming to the States of Jersey Police and pointing out where he created the holes," the spokeswoman added.
Forensic examinations are still going on in two other chambers. Numerous finds have been made and are being studied, police say. A first chamber has already revealed a blood-spattered stone bathtub, apparently corroborating former pupils' evidence.
Earlier this month, extensive tests showed fragments of a child's skull found under concrete had been there since the 1920s.
The building first opened as an Industrial School for Boys in the 1850s.
So far only one person has been charged in connection with the investigation, though more than 40 suspects have been identified and more arrests are expected.