Bahmani Ahmadi: Police questioned and released sex offender in 2012

Bahmani Ahmadi used social media to groom some of his victims

A "dangerous" sex offender convicted of a string of child sex crimes was questioned and released by police more than two years earlier, it has emerged.

Bahmani Ahmadi, 22, is awaiting sentencing after admitting 18 charges, including sexual assault and grooming.

Northumbria Police said he was arrested and released without charge in 2012 after complaints he had sex with a 15-year-old-girl from a care home.

The force said he had subsequently been convicted of the offence.

Temporary assistant chief constable Debbie Ford said: "We did investigate him at the time, but at the time we found there was no case to answer and we didn't take it any further forward."

Ahmadi was questioned but a senior officer decided that no further action should be taken and the case was not referred to the Crown Prosecution Service.

Ahmadi, of Hampstead Road, Benwell, was arrested in 2014 as part of Operation Sanctuary - a police inquiry into the sexual abuse and grooming of vulnerable young women on Tyneside.

The force said it was "trying to understand" why no charges were brought in 2012

Ms Ford said: "We are going to look at the investigation into the case, our professional standards department are investigating that matter now and it's difficult for me to comment any further in relation to how that investigation may pan out in the future.

"We're trying to understand the reasons why the investigation was concluded without any charges being brought back in 2012.

"I would assure the public we will do everything we can to make sure that that investigation is carried out thoroughly and properly and if any issues arise from that investigation, they will be dealt with robustly."

The force is continuing to investigate Ahmadi, who "relentlessly" pursued victims as young as 11 online.

He posed as a 14-year-old named Holly to befriend his targets and plied many of them with alcohol.

Northumbria Police Det Supt Steve Barron said he was "possibly the most dangerous person" he had come across in 22 years of policing.

Ahmadi will be sentenced in July at Newcastle Crown Court.