Detectives leading a criminal investigation into the Hillsborough disaster have appealed for 19 people seen in CCTV footage at the stadium to come forward.

New images showing the potential witnesses at the Leppings Lane end of the football ground in Sheffield have been released by Operation Resolve as part of its inquiry into the disaster and the events that led to the deaths of 96 Liverpool fans.

Operation Resolve is one of two criminal investigations launched after the publication of the Hillsborough Independent Panel’s report in 2012.

The investigating team has released footage and still images of 19 people they want to speak to who can be seen in the area of gate C when it was opened at 2.52pm on 15 April 1989.

The footage includes computer-generated images of the Leppings Lane end of Hillsborough stadium as it would have looked 27 years ago, and specialists have used recognition techniques to find different images of some of the potential witnesses.

DCS Neil Malkin, the senior investigating officer, said he hoped the people identified in the footage would be able to help.

Speaking outside Hillsborough, he said: “The appeal today is for 19 individuals seen outside gate C at 2.52pm on the 15 April 1989.

“These people were in close proximity to the gate at the time that it opened and I would like to hear from these people because they might be able to provide me with information that could assist me in my inquiry.”

Malkin said the 19 people were in the “right place at the right time” and may be able to identify others.

DCS Neil Malkin, the senior investigating officer of Operation Resolve, one of two criminal investigations into the deaths of 96 people at the Hillsborough stadium. Photograph: Danny Lawson/PA

He said: “They might know people they were with or may be able to shed some light on others that were present at the time.

“It’s important because we need to understand the full facts around the opening of gate C at 2.52.

“It’s a significant piece of work that I am undertaking at the moment and these people would be helpful to add value to what I have already undertaken.”

He added: “It’s their experience. Who they were with, their entry and how they came to be at gate C at that time and really their experience of entering through gate C and what they did, what they saw, what they heard.”

The detective said anyone who contacts the investigating team will be treated with sensitivity.

He said: “We will try and understand their concerns. It’s very difficult after 27 years to understand the difficulties people face. Some may face not looking at images or may not want to recount their experience but nevertheless we’ve got people who can help to overcome that.”

In April, an inquest jury concluded the 96 victims were unlawfully killed and that blunders by South Yorkshire police “caused or contributed to” the disaster.

Malkin said Operation Resolve, which has already interviewed more than 1,200 people who entered the stadium through gate C when it opened, was on target to submit full files of evidence to the Crown Prosecution Service by the turn of the year.

• Anyone who recognises any of the people identified in the CCTV footage is asked to contact Operation Resolve on 0800 0 283284 or through the website http://www.operationresolve.co.uk