Video report by ITV News Correspondent Lucy Watson, at the scene in Berkshire
The father of Pc Andrew Harper has said the family are "devastated" following his death.
In the first brief comments from the family, Philip Harper said: "We're absolutely devastated and we're in a bad place."
He spoke as detectives continued to question ten people aged between 13 and 30 remain in custody over the death of Pc Harper, a newlywed police officer killed after being dragged along by a vehicle.
The Thames Valley Police officer, who was responding to a reported burglary in Berkshire, died following a "serious incident" on Thursday.
On Saturday, forensics officers were seen searching a caravan site on Padworth Road around three miles away from the scene, with two vans appearing to block the entrance.
In an update given near the scene, Thames Valley Police spokesman Jack Abell said an emergency call was made reporting a burglary at a residential property at 11.18pm on Thursday.
An officer on duty with Pc Harper was not physically injured but is being provided with emotional support, he added.
Police are currently focusing their inquiries on one vehicle, understood to be a Seat.
The police cordon has been extended by around 100 metres as around 10 white-suited forensics officers conduct a sweep of the area.
The 28-year-old Pc Harper, who has been described by his uncle as the "loveliest person that you will ever meet", married his wife Lissie just four weeks ago.
Photographs of the pair on their wedding day at Ardington House, a Georgian manor in Oxfordshire, have been released.
In one picture the couple can be seen smiling as they cut their wedding cake with a sign next to them reading "happily ever Harper".
Tributes from Pc Harper's family have been left on Facebook with his grandmother, Maureen Shrimpton, writing: "Just a really horrible day.
"Our grandson Andrew was killed last night while doing his police work. So proud of him. Our love goes to his lovely wife, Mum and Dad, brother and all of his family and friends. Love from Nan and Bubba xxx"
His uncle Dale Shrimpton posted: "He's my oldest Nephew. My sister's first born. Mum and dad's first grandson... And was married two weeks ago at a dream wedding. We are devastated.
"He was the loveliest person that you will ever meet. I cant begin to tell you how we feel."
Thames Valley Police Chief Constable John Campbell said: "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."
He added that the force's flags would fly at half mast "in honour and memory of Andrew".
A post-mortem examination to establish his cause of death is underway.
Pc Harper joined as a special constable in 2010 before becoming a police officer a year later, serving in the Roads Policing Proactive Unit based at Abingdon Police Station.
On Friday, forensic investigators could be seen gathering items that lay on the road and taking photographs.
Two white tents have also been erected.
Prime Minister Boris Johnson has said he is "shocked and appalled" by the death of "a brave officer".
He added: "My thoughts are with PC Harper's family, friends and colleagues at this terrible time.
"It is the most powerful reminder that police officers up and down the country put themselves at risk every single day to keep us safe.
"They have my absolute support."
Home Secretary Priti Patel said: "I'm devastated and appalled by the tragic death of Pc Andrew Harper and my thoughts are with his loved ones, colleagues and the community he served with great pride at this immensely difficult time.
"Pc Harper died in the line of duty protecting the public and his incredible bravery and extraordinary sacrifice will not be forgotten."