Detectives have confirmed they are investigating 76 new cases of suspected historical abuse at children's care homes in north Wales.
Police officers leading Operation Pallial say the allegations centre on 18 different care homes between 1963 and 1992.
A total of 84 individuals have been named as abusers by complainants and 16 of those have been named by more than one victim. One arrest has so far been made.
The total number of allegations recorded since the new police inquiry was launched in November has now risen to 140.
The alleged victims were aged between seven and 19, while the offences range from verbal and physical assaults and abuse through to indecent assaults and serious sexual assaults.
Detective Superintendent Ian Mulcahey said: "Almost everyone that Operation Pallial is aware of has now been video interviewed by specially trained officers.
"Many have provided graphic accounts of abuse, in some cases of very serious criminality."
North Wales Chief Constable Mark Polin said it was "never too late" to report abuse and urged anyone who has not come forward yet to do so.
He also told offenders they should look over their shoulders.
He said: "If you believe that the passage of time will reduce the resolve of Operation Pallial or any police force to identify people still alive who have caused harm to others and bring them to justice, you are are sorely mistaken.
"People who commit serious and sexual offences should live with the knowledge that we will always examine new information and evidence and seek to bring them to justice for their crimes.
"Offenders should quite rightly have to look over their shoulders for the rest of their lives."
One of the victims who has taken new allegations to the police has previously told Sky News how he was abused in various North Wales care homes.
"Michael" also revealed how as a 12-year-old he was repeatedly put on a mini-bus with other children, driven down to London and forced to take part in lurid sex parties.
Last November, he told Sky News how the men who abused him were all "posh people" who plied the boys were drink and drugs before abusing them.
He said: "It was how compliant you were, how nice you were towards them and looking back it was all about what they could get away with."
The Waterhouse Inquiry in 2000 found evidence of widespread sexual abuse and several care home staff members were convicted for various offences.
Compensation was then paid to 140 victims but there have been long held suspicions that the true extent of abuse in the homes in north Wales has never been uncovered.
Operation Pallial was set up to ensure allegations were indeed properly investigated.
Police said the first phases of the work "has resulted in the collection of significant evidence of systemic and serious sexual and physical abuse of children whilst in care".
It has also shown "no evidence of systemic of institutional misconduct by North Wales Police officers or staff".
Last week, detectives made their first arrest as part of the investigation into historical allegations of abuse.
A man was arrested in Ipswich, Suffolk and questioned on suspicion of a number of serious sexual offences before being bailed to until the end of July.
Officers expect phase two of the operation to involve further arrests.
The NSPCC said the inquiry was "a major step forward into probing claims of widespread child abuse".
The charity's director Peter Watt added: "Many who have been waiting decades for justice and for their voices to be heard have now finally found the courage to come forward and we mustn't fail them this time."
The NSPCC urged anyone who has any information about abuse to contact either its round-the-clock helpline on 0800 389 6176, or the police immediately.
The full police report into phase one of the inquiry has been published on the North Wales Police and Serious Organised Crime Agency ( Soca ) websites.