The Metropolitan Police officer suspected of kidnapping and murdering Sarah Everard was taken to hospital for a head injury sustained while in custody.
Scotland Yard said the suspect, who is in his 40s, was treated, discharged and returned to the police station where he is being held.
He was found collapsed and unconscious in his cell on Thursday after suffering serious head wounds, according to the Sun.
The Met said: “The suspect was taken to a hospital for treatment to a head injury sustained while in custody.
“He has since been discharged and returned to custody. We are not prepared to discuss further.”
Met Commissioner Dame Cressida Dick said on Wednesday night that human remains – which have not yet been identified – had been found in an area of woodland in Ashford, in Kent, by detectives investigating Ms Everard’s disappearance.
The officer, who is in the Parliamentary and Diplomatic Protection Command, was held on Tuesday night on suspicion of kidnap before being further arrested on suspicion of murder and a separate allegation of indecent exposure the following day.
On the day of Ms Everard’s disappearance, he was reportedly working a 2pm to 8pm relief shift at the US Embassy in Nine Elms, south-west London, around three miles from where she was last seen.
According to unconfirmed reports, detectives are investigating whether he might have used his warrant card to entice Ms Everard towards his car before snatching her.
A woman in her 30s has been arrested on suspicion of assisting an offender.
Officers removed vehicles from outside a house being searched in Deal, Kent, where the officer is believed to have lived with his wife and two children.
Prime Minister Boris Johnson said he was “shocked and deeply saddened”, adding: “We must work fast to find all the answers to this horrifying crime.”
The events have prompted an outpouring of shock and anger as women across the country shared their own experiences of feeling unsafe.
And London Mayor Sadiq Khan admitted the capital’s streets are not safe for women or girls when asked by LBC’s Shelagh Fogarty: “London’s streets are not safe for women, are they?
He said: “No, they aren’t – or for girls – and it’s really important that people of my gender understand that.
“If you’re a woman or a girl, your experiences of our city, in any public space, whether it’s in the workplace on the streets, on public transport is very different to if you are a man or a boy, and it’s really important that people like me in positions of power and influence understand that and take steps to address that.”
A vigil called “Reclaim these streets” is due to take place at Clapham Common bandstand in south London on Saturday.
Meanwhile, MPs listened in silence as Labour’s Jess Phillips read out the names of women killed in the UK where a man has been convicted or charged as the primary perpetrator.
The MP for Birmingham Yardley spent more than four minutes listing the names of the almost 120 victims from the last 12 months.
After finishing the list, Ms Phillips said people had “prayed that the name of Sarah Everard would never be on any list” and urged everyone to work to ensure “nobody’s name ends up on this list again”.
Home Secretary Priti Patel said “every woman should feel safe to walk our streets without fear of harassment or violence” after Dame Cressida sought to reassure the public.
“It is thankfully incredibly rare for a woman to be abducted from our streets,” Dame Cressida said.
“But I completely understand that, despite this, women in London and the wider public – particularly those in the area where Sarah went missing – will be worried and may well be feeling scared.”
Ms Everard vanished while walking home from a friend’s flat in south London on March 3.
She is thought to have walked through Clapham Common towards her house in Brixton – a journey which should have taken around 50 minutes.
Ms Everard was last captured on a doorbell camera walking along the A205 Poynders Road towards Tulse Hill at around 9.30pm.
The diplomatic protection squad is responsible for guarding the Parliamentary estate, including Downing Street and the Palace of Westminster, as well as embassies in London.
The suspect’s main job was uniformed patrol of diplomatic premises, according to the Met, who said he was not on duty at the time of Ms Everard’s disappearance.
Dame Cressida said his arrest “has sent waves of shock and anger through the public and through the whole of the Met.”
She said: “I speak on behalf of all my colleagues in the Met when I say we are utterly appalled at this dreadful news. Our job is to patrol the streets and to protect people.”
The commissioner said people living around the Clapham and Tulse Hill areas of south London could expect to see increased patrols in the area.