The child sexual abuse scandal that rocked a central city in the United Kingdom when it erupted four years ago appears to be worse than originally believed.

New figures by the National Crime Agency (NCA) put the number of children believed to have been sexually exploited in the town of Rotherham over 16-year period at an astonishing 1,510 – up from the 1,400 figure identified in a 2014 report.

At least 1,300 were female, detectives said Tuesday, the BBC reported.

A previous report commissioned by the Rotherham Council in 2014, found that at least 1,400 children – “a conservative estimate” – had been sexually exploited in the South Yorkshire city between 1997 and 2013.

According to the 2014 report, children as young as 11 were “raped by multiple perpetrators, abducted, trafficked to other cities in England, beaten and intimidated.”

Police said the victims were plied with drugs and alcohol before being abused at parties, in taxis or in back rooms. The vast majority of the victims were white British girls ages 11 to 19.

The NCA is conducting an independent investigation called Operation Stovewood at the request of the South Yorkshire Police.

In its new findings, the NCA said it has identified 110 suspects of being part of child-grooming gangs in Rotherham. About 80 percent of the suspects identified are of South Asian Muslim backgrounds, the Guardian reported.

“(Operation Stovewood is) a unique and unprecedented investigation, challenging in its scale and complexity,” said Paul Williamson, senior investigating officer with the NCA. “The momentum and pace of the inquiry is increasing and that will continue to increase. Justice is being rendered and I’ve got a very, very committed team that’s working on a very worth mission.”

The NCA said 35 individuals have been arrested, 18 have been charged and four have been convicted.

Of 1,510 potential victims, detectives said they have spoken to about 260 of them. Their aim is to speak to every victim, police said.

The South Yorkshire Police launched its own investigation – Operation Clover – in August 2013 to investigate the child sexual abuse cases. As a result, 19 men and two women have been convicted in 2016 and 2017 of sexual offenses.

One of the ringleaders, identified as Arshid Hussain, was convicted of 23 charges of rape and indecent assault. He was sentenced to 35 years in prison.

Police in Rochdale, Oxford and Newcastle have also had its own child sexual abuse scandals in recent years whose crimes follow a pattern that are grimly familiar to those in Rotherham.

Some allege that the crimes were long ignored by authorities afraid they would be branded racist or fearful the allegations might inflame ethnic tensions.

The Associated Press contributed to this report.