The number of investigations into the response by police to allegations of child sexual abuse in Rotherham has increased to nearly 100, the police watchdog has said.

The Independent Office for Police Conduct (IOPC) said on Wednesday that at the beginning of April it was overseeing 98 investigations into the response of South Yorkshire police, compared with 62 at the same point last year.

IOPC said 45 of those inquiries been completed and 33 current and former police officers were still being investigated. The body will publish an overarching report once Operation Linden, which is examining allegations of misconduct by police in relation to child sexual exploitation in Rotherham, has concluded.

The watchdog confirmed that some of the completed investigations had identified potential misconduct by officers, but said the outcomes of individual investigations would not be made public until the final report was published.

An investigation by the Times in 2012 found that gang rape and trafficking were widespread in Rotherham. A subsequent report in 2014 by Prof Alexis Jay, a former chief inspector of social work, concluded that failures of political and police leadership had contributed to the sexual exploitation of 1,400 children by groups of Asian men in the town over 16 years.

Jay concluded that police gave no priority to child sexual abuse, regarded many victims with contempt and failed to act on their reports of abuse.

The 98 Operation Linden investigations include an inquiry into whether the former South Yorkshire police and crime commissioner Shaun Wright lied under oath when giving evidence to the home affairs select committee in 2014. Wright told MPs he had not been aware that child sexual exploitation was a significant problem during his time as head of Rotherham’s children’s services.

The increase in the number of investigations under Operation Linden is the result of new complaints being received and decisions to split some investigations to make them more manageable.

Steve Noonan, acting deputy director of major investigations at the IOPC, said: “We are supporting 53 survivors and a number of complainants through a very difficult period, when they are also being asked to give evidence to the National Crime Agency to support their investigations into the terrible crimes committed in Rotherham.

“We would like to thank the survivors and everyone affected by our investigations for their patience and cooperation while we continue with this very important work.”

Operation Linden is the second largest independent investigation the IOPC has carried out, after its inquiry into South Yorkshire police’s conduct over the Hillsborough disaster. The operation has a dedicated team of 35 staff who have analysed more than 15,000 documents and pieces of evidence, some of which date to the 1990s.

“The timeframes involved are very challenging and in a significant number of cases we are unable to identify the officers involved,” Noonan said. “However, even where we’ve been unable to identify officers, we will still conclude our investigations to see if any conduct or learning can be identified.

“We will publish an overarching report combining the outcomes of our investigations when they are all complete. Our aim is to not only highlight any conduct matters relating to individual officers but, crucially, to share our understanding of why such serious allegations often weren’t investigated and how this can be avoided in the future.

“Ultimately, we want those affected to be confident that their complaints have been comprehensively investigated, and for South Yorkshire police and indeed all forces across the country to learn from our findings.”