Five years on from the collapse of Didcot Power Station's boiler house and the demolition industry still does not know how to avoid a similar disaster in future.
Demolition workers Michael Collings, Ken Cresswell, Christopher Huxtable and John Shaw were killed on February 23, 2016, by the partial collapse of the boiler house on site.
Thames Valley Police and the Heath and Safety Executive launched a joint investigation shortly afterwards into suspicions of corporate manslaughter, gross negligence manslaughter and health and safety offences.
It took more than six months for their bodies to be recovered, prompting criticism from their families at the time.
The editor of Demolition News, Mark Anthony, said there was concern in the industry that no preliminary report had been produced yet.
He told the BBC: "Here we are five years on no closer to understanding what caused it - there have been no prosecutions, no preliminary reports.
"There are still four families out there that have got no closure - no clue as to why their loves ones didn't return home that day.
"The industry itself has no clue as to what it might do differently to avoid a repeat."
Read also: Tribute to Didcot Power Station demolition workers
Last year Thames Valley Police working with the Health and Safety Executive, collected more than 150,000 pieces of digital evidence and more than 4,500 physical exhibits including 1,870 tonnes of structural exhibits to be examined.
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