Five police officers are under investigation for manslaughter after the death of a 24-year-old man in police custody earlier this month. Brian Ringrose, from Milton Keynes, was placed in an induced coma and died in hospital days after he was arrested by Thames Valley police on 27 January. The Independent Office for Police Conduct said it was investigating the use of a “flexible lift and carry system” (Flacs) used to transport Ringrose to a police van when he was restrained using handcuffs and limb restraints. The Guardian has requested more information from the National Police Chiefs Council on what Flacs is and how it is used. The IOPC said officers had medical concerns for Ringrose when he was initially arrested and requested an ambulance, which took him to Milton Keynes University hospital. After Ringrose was discharged officers restrained him in the hospital before taking him into custody in a police van, but his health deteriorated en route and he was returned to hospital. There he was placed in an induced coma and died on 2 February. A postmortem recorded the cause of death as inconclusive pending further investigation. Thames Valley has suspended its use of Flacs equipment while the investigation is carried out, and the IOPC is working with the National Police Chiefs Council to establish how it is used by other police forces. The five officers from Thames Valley Police are under investigation for suspected gross negligence manslaughter and unlawful act manslaughter, and one is also being investigated for suspected common assault. They have also been served with gross misconduct notices for potential breaches of professional behaviour related to use of force. The IOPC said: “The decision to inform officers they are under criminal investigation means evidence indicates a criminal offence may have been committed. This does not necessarily mean criminal charges will follow.” Its investigation will determine whether the matter is referred to the Crown Prosecution Services. Graham Beesley, IOPC regional director for the south-east, said: “Our thoughts are with Mr Ringrose’s family and all of those affected by his tragic death. This is a significant development in our investigation and is based on evidence we have gathered to date. We have updated Mr Ringrose’s family and will now seek to interview the officers under criminal caution. “It is our role to independently investigate all of the circumstances when someone dies in police custody.” Thames Valley police said: “We have been fully co-operating with the IOPC from the outset and will continue to do so. Support is being given to the officers involved.”