PC Andrew Harper died of multiple injuries and the 10 people being held over his death were arrested at a caravan park, police have said.
PC Harper, 28, was dragged along the road by a vehicle after responding to a "serious incident" in the Berkshire village of Sulhamstead at about 11.30pm on Thursday.
A post-mortem yesterday showed PC Harper died of multiple injuries.
Detective Superintendent Ailsa Kent, of Thames Valley Major Crime Unit, told reporters: "The cause of death is consistent with our current belief that Andrew was caught between a vehicle and the road and then dragged for a distance."
Det Sup Kent said it remains unclear how PC Harper "came to be out of his vehicle and then caught under the suspect vehicle".
She said: "What we do know is that Andrew and his crewmate were attending a reported burglary in Bradfield Southend.
"While responding, the officers located a vehicle that was suspected to be involved in the burglary, in Lambdens Hill."
Officers have been granted permission to keep the group - boys and men aged between 13 and 30 - in custody for a further 36 hours.
The father of Pc Andrew Harper has said that he and his family have been left ‘devastated’ by the loss of their son.
Pc Harper, 28, who married just four weeks ago, was responding to a burglary report when he was dragged by a vehicle along the A4 Bath Road in Berkshire for several hundred yards.
Police are continuing to search a caravan site three miles from where a police officer was killed on Thursday.
Ten people between the ages 13 and 30 remain in custody and are being quizzed by police.
Pc Harper, who was born in Oxford, had been together with his wife Lissie for 10 years before they got engaged in Italy in May 2017, and had been due to go on their honeymoon in a few days.
Philip Harper told Sky News: "We're absolutely devastated and we're in a bad place."
Thames Valley Police have been focusing on the Four Houses Corner Caravan site on Padworth Road since Friday, with two vans appearing to block the entrance.
Forensic officers in white overalls conducting searches on Saturday at the site, described as a traveller site on the ‘Run by West Berkshire’ authority's website.
Thames Valley Police said it was still trying to establish the exact chain of events that led to PC Harper's death.
The force said PC Harper had attended the reported break-in with a fellow officer.
Thames Valley Police Chief Constable John Campbell said the death of PC Harper had left the entire force "shocked and saddened".
Officers stationed at the scene laid flowers in tribute on Saturday morning near two tents erected on Ufton Lane.
Mr Barber said: “Many people will have only heard the news yesterday and it does hit hard the morning after.
“You realise this is the second morning Andrew’s family will wake up without him.
“It’s a personal tragedy for them first and foremost and will leave a lasting impression on the force and the surrounding community.”
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Several residents living nearby in cottages and farmhouses said they had not had any problems with thieves targeting their property.
One officer stationed at the site said: “I think it’s something every officer feels.
“We’ve all had situations where you’re in danger responding to incidents like that.”
Mr Campbell said PC Harper was a "highly regarded, popular member of the team", adding: "Everybody I've spoken to about Andrew talked about the incredible personality he was, what a fantastic police officer, and what a great friend and man he was, and he'll be sorely missed by everybody.
"My thanks go to all those staff and officers who attended this incident, as well as our colleagues at the fire service and also the ambulance service for their professionalism and support at what you can imagine was obviously a distressing scene."
Friends and family paid emotional tributes to PC Harper on Facebook on Friday using the “thin blue line” replacing the profile image.
“Such horrible news,” one person wrote, “Sending our condolences to you and your sister and family.”
“I’m Sorry for the loss of your colleague and friend buddy,” another person wrote on PC Harper’s friend’s profile picture, “My thoughts are with you.”