The deaths of four men in the Didcot power station collapse are the subject of a police manslaughter investigation, an inquest heard.
Christopher Huxtable, 33, from Swansea, South Wales, Kenneth Cresswell, 57, and John Shaw, 61, both from Rotherham, South Yorkshire and Michael Collings, 53, from Saltburn-by-the-Sea, Teesside, died after the partial collapse of the boiler house at the Didcot A plant in Oxfordshire on February 23 2016.
A pre-inquest review at Oxford Coroner's Court heard that Thames Valley Police and the Health and Safety Executive have launched a joint investigation to consider corporate manslaughter, gross negligence manslaughter and health and safety offences.
Detective Chief Inspector Craig Kirby, the senior investigating officer, told the inquest he did not know how long the inquiry would take, but an "initial advice file" had been passed to the Crown Prosecution Service.
"A dedicated police and Health and Safety Executive major incident room continues to investigate corporate manslaughter, gross negligence manslaughter and serious health and safety at work offences," he said.
"The investigation team continues to meet regularly with a specialist prosecutor from the Crown Prosecution Service and a lead legal adviser from the Health and Safety Executive to quality assure our work and ensure that all lines of inquiry are robustly explored.
"Whilst it is not possible to give any estimated completion date due to the complexity of the investigation and the volume of material being examined, an initial advice file was submitted to the Crown Prosecution Service on December 29 2017 for their consideration and investigative advice.
"The on-site evidence recovery continues to be a key line of inquiry to understand why the boiler house collapsed."
Mr Kirby added: "To date some 1,921 witness statements have been taken by the investigation team.
"As the investigation has progressed, a number of significant witnesses have been identified and interviewed.
"A number of individuals and companies suspected of committing offences have been identified and voluntarily interviewed under caution."
Oxfordshire coroner Darren Salter said that when he opened inquests into the deaths of the four men last year, post-mortem examinations had given their cause of death as multiple injuries.
Mr Salter told the hearing that the decision to resume the inquests would depend on the outcome of the on-going criminal investigation.
Speaking after the hearing, James Howard, a director of demolition contractor Coleman & Company, said the firm had commissioned its own investigation into the cause of the tragedy.
"We believe the findings highlight industry-wide practices that need to be challenged and reviewed," he said.
"We now consider it essential to share this learning as a matter of urgency, so that immediate steps can be taken within the industry to prevent future loss of life and so that the families can begin to understand what caused this dreadful accident."
Mr Howard said the firm would be writing to the police, HSE and the coroner to share the preliminary findings of the investigation.
"The loss of Chris, John, Kenny and Mick has been felt deeply by everyone at Coleman & Company and this tragic accident has had a profound effect on the health and well-being of many of us over the past two years," he added.