MORE people will be interviewed under caution in the coming months as a multi-million pound investigation into the collapse of the Didcot power station continues.

Two years on from the tragedy, the families of the four men who died are still waiting for answers to what caused part of the boiler house to collapse as it was being prepared for demolition.

UPDATE - Didcot pays its respect two years on 

Giving an update on the case, Thames Valley Police (TVP) and the Health and Safety Executive (HSE) have conceded that they never expected it to go on so long but said the complexity of the incident and the amount of evidence was 'almost unprecedented'.

Ken Cresswell, 57, John Shaw, 61, both from Rotherham, Michael Collings, 53, from Teesside, and Christopher Huxtable, 34, from Swansea died when units one and two of the boiler house collapsed.

Police are still considering bringing charges of corporate manslaughter, gross negligence manslaughter and serious health and safety at work offences.

Assistant Chief Constable Jason Hogg, the gold commander for the operation, said: "We have interviewed a number of parties under caution.

"I have no doubt in the months to come we will be seeking to interview additional people for potential criminal offences.

"From the evidence we have gathered we think there's sufficient grounds to conduct a criminal investigation but that will be a matter for the Crown Prosecution Service."

A 24 hour police presence on the site is expected to cease at the end of March by which time remaining work on the boiler house will have been completed.

At this point owners RWE will be given back control of the site to decide what to do with it next.

ACC Hogg said the investigation has so far cost 'several million pounds', one of the most expensive it has ever carried out.

Following a pre-inquest review hearing earlier this month contractors Coleman and Company said it had concluded its own investigation and already knew the reasons for the collapse.

These findings will be shared with the police by the end of March 2018.

Peter Baker, HSE's director of construction, said: "In our experience the reasons for a major incident of this sort are often several fold.

"There are the immediate causes on the day but also a significant number of underlying causes including management decisions, technical issues and behaviour of staff.

"As part of the investigation we have to look at all lines of enquiry.

"We haven't identified anything that is particularly unique or dangerous that we need to alert the industry to at the moment but we remain alert to that as we go on."