FAMILIES of those killed when Didcot Power Station collapsed are still waiting for answers three years on from the tragedy.

At 4.04pm this afternoon, Oxfordshire will once again remember the terrible events of February 23, 2016 when four men were crushed to death as the building they were working on came down around them.

Investigators have revealed they are analysing 870 tonnes of evidence collected from the site and are doing 'everything in their power' to uncover what happened.

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But, as another year since the disaster passes, there is growing frustration at a perceived lack of progress with town leaders saying they desperately want to draw a line under the events.

READ MORE: How the tragedy unfolded

Former power station worker Des Healy, who was mayor at the time of the collapse, said: "We want to know why it happened and who will take responsibility.

"That has been on my mind every day since the beginning and nothing will change until people get the answers they deserve.

"There is a lot of frustration and a lot of questions.

"I have been asked half a dozen times in the last few weeks what's happening and my answer is always the same: 'I have no knowledge of anything'.

"We are in the dark and time is going on."

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Workers Ken Cresswell, 57, John Shaw, 61, both from Rotherham, Michael Collings, 53, from Teesside, and Christopher Huxtable, 34, from Swansea, died in the incident after part of the boiler house came down as it was being prepared for demolition.

It took more than six months to recover all the bodies and police maintained a constant presence on the site until March last year when it was handed back to owners RWE.

READ ALSO: Timetable confirmed for demolition of three remaining cooling towers

Thames Valley Police and the Health and Safety Executive have been reluctant to reveal much detail due to the sensitivity of the ongoing investigation and the possibility that trials will be held in future.

In a statement released to mark the anniversary TVP Assistant Chief Constable, Jason Hogg, said 870 tonnes of evidence has now been moved to a special facility in Buxton, Derbyshire for further forensic examination.

Several interviews with potential suspects have already been conducted and more are planned over the coming months as the force continues to investigate potential manslaughter and health and safety offences, according to Mr Hogg.

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He added: "We continue to express our deepest sympathies to the families and friends of Michael Collings, Ken Cresswell, Christopher Huxtable and John Shaw who died following the partial collapse at Didcot Power station.

WATCH: Police press conference from last year

“Our thoughts also remain with those who were injured as well as the community following this tragic incident.

“Thames Valley Police along with our colleagues at the Health and Safety Executive remain committed to obtaining answers and justice for those who have been affected.

“A team of experts from HSE and Thames Valley Police, supported by independent scientific experts, continue to analyse thousands of exhibits and work through complex technical data which takes significant time to analyse and interpret.

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“Further detailed interviews of both witnesses and potential suspects are also planned to further progress the investigation.

“Due to the complexity of the investigation we are working closely with the Crown Prosecution Service to make sure that all appropriate lines of enquiry are fully explored.

“We continue to provide support and updates on our progress to the families and I would like to reassure them that our focus and commitment to this investigation has not changed.

“We are doing everything in our power to obtain the answers that they so rightly deserve as quickly as we are able, balanced with our duty to explore all avenues to obtain those answers.”

Commemorations in Didcot itself are set to be more muted than in previous years with private reflection taking the place of memorial events.

Current mayor Bill Service said a decision had been taken last year not to formally mark this anniversary in order to give the town a chance to move on.

But with the investigation still hanging over residents, this is a difficult thing to achieve, according to Mr Service.

He added: "The amount of time the investigation is taking is really frustrating for everyone concerned, particularly the families - they need closure.

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"But we were told at the start it might take five years to get to the bottom of it.

"From a personal point of view, I will be taking a moment to reflect and I'm sure many people will be doing the same."

As the investigation continues, plans are progressing to resume demolition of the Didcot A site with RWE expecting the job to be complete by the end of the year.

READ AGAIN: High tech IT project could be built next to power station

Staff from the power company are planning to lay flowers on the site today in memory of those who died.

A spokeswoman said: "They remain in our thoughts and we remember them and their families, especially at this difficult time.

"We would like to thank all the emergency services who supported in the difficult recovery operation and also for their treatment of those who were injured.

"We continue to provide our full support to the on-going joint police and HSE investigation."