Thames Valley police would not comment on whether any of the suspects reside at the caravan site but said: "This police presence forms part of the investigation following the death of PC Andrew Harper".
Richard Benyon, Conservative MP for Newbury, added: 'We don't fully know what has happened but this is an absolute tragedy for Andrew Harper's family and loved ones.
Officers are carrying out house to house inquiries, reviewing CCTV footage, interviewing witnesses and conducting forensic examinations, Det Supt Kent added. And was married two weeks ago at a dream wedding.
"The murder of PC Andrew Harper is a mindless and a brutal crime", he stated.
The incident happened at the crossroads of Ufton Lane and Lambdens Hill, near to Sulhamstead at around 11.30pm.
The 28-year-old policeman's grandmother, Maureen Shrimpton, added her own tribute, saying: "Just a really frightful day".
Mr Campbell extended his thanks to the officers and other emergency services who attended the incident for their support and professionalism at what was an "obviously distressing scene".
The Prime Minister called the incident a "powerful reminder" of the risks police officers take.
He said the force's flags are flying at half mast as a sign of respect "in honour and memory of Andrew".
Cops were photographed searching the inside of a gray BMW near the scene of the robbery Friday morning, according to the paper.
The force also refused to comment on a report which suggested that Harper was hit by a second police auto which was responding to the incident.
"I am deeply shocked and appalled by the death of a courageous officer on duty in Thames Valley last night", Prime Minister Johnson said on Twitter.
Days later, a 42-year-old West Midlands Police officer was run over by his own patrol vehicle in Birmingham after it was stolen by a suspected auto thief, with the officer suffering serious injuries to his pelvis and head.
This came just days after Metropolitan Police constable Stuart Outten, 28, was left with head and hand injuries after challenging a motor offences suspect allegedly armed with a machete in Leyton, east London.
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